diff --git a/discord_rss_bot/main.py b/discord_rss_bot/main.py
index e59d6f7..6693c82 100644
--- a/discord_rss_bot/main.py
+++ b/discord_rss_bot/main.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import concurrent.futures
 import io
 import json
 import logging
@@ -15,6 +16,7 @@ from datetime import datetime
 from functools import lru_cache
 from html import escape
 from html import unescape
+from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import Annotated
 from typing import TypedDict
@@ -61,6 +63,7 @@ from discord_rss_bot.custom_message import get_message_username
 from discord_rss_bot.custom_message import replace_tags_in_text_message
 from discord_rss_bot.custom_message import save_embed
 from discord_rss_bot.feeds import FeedUpdateError
+from discord_rss_bot.feeds import JsonValue
 from discord_rss_bot.feeds import SentWebhookRecord
 from discord_rss_bot.feeds import coerce_media_gallery_image_limit
 from discord_rss_bot.feeds import coerce_webhook_text_length_limit
@@ -91,12 +94,15 @@ from discord_rss_bot.git_backup import commit_state_change
 from discord_rss_bot.git_backup import get_backup_path
 from discord_rss_bot.is_url_valid import is_url_valid
 from discord_rss_bot.search import create_search_context
+from discord_rss_bot.settings import data_dir
+from discord_rss_bot.settings import default_custom_embed
+from discord_rss_bot.settings import default_custom_message
 from discord_rss_bot.settings import get_reader
+from discord_rss_bot.settings import make_app_reader
 
 if TYPE_CHECKING:
     from collections.abc import AsyncGenerator
     from collections.abc import Iterable
-    from pathlib import Path
 
     from reader.types import JSONType
 
@@ -2649,12 +2655,439 @@ async def manual_backup(
     return RedirectResponse(url=f"/?message={urllib.parse.quote(message)}", status_code=303)
 
 
+def _get_grouped_feeds(reader: Reader) -> list[dict[str, typing.Any]]:
+    """Build a list of webhook groups with pre-computed indices for template use.
+
+    Each group dict contains:
+        name: The webhook name (or "Orphaned (no webhook)").
+        group_idx: 1-based index for the group.
+        feeds: List of dicts with:
+            feed: The Feed object.
+            feed_idx: 1-based index within the group.
+
+    Returns:
+        list[dict]: Grouped feeds with pre-computed indices for template rendering.
+    """
+    hooks: list[dict[str, str]] = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+
+    feeds_by_webhook: dict[str, list[Feed]] = {}
+    orphaned: list[Feed] = []
+
+    for feed in reader.get_feeds():
+        feed_webhook: str = str(reader.get_tag(feed.url, "webhook", ""))
+        hook_name: str = ""
+        for hook in hooks:
+            if hook["url"] == feed_webhook:
+                hook_name = hook["name"]
+                break
+        if hook_name:
+            feeds_by_webhook.setdefault(hook_name, []).append(feed)
+        else:
+            orphaned.append(feed)
+
+    grouped: list[dict[str, typing.Any]] = []
+    for group_idx, (name, feed_list) in enumerate(feeds_by_webhook.items(), start=1):
+        grouped.append({
+            "name": name,
+            "group_idx": group_idx,
+            "feeds": [{"feed": f, "feed_idx": idx} for idx, f in enumerate(feed_list, start=1)],
+        })
+    if orphaned:
+        grouped.append({
+            "name": "Orphaned (no webhook)",
+            "group_idx": len(grouped) + 1,
+            "feeds": [{"feed": f, "feed_idx": idx} for idx, f in enumerate(orphaned, start=1)],
+        })
+
+    return grouped
+
+
+@app.get("/mass", response_class=HTMLResponse)
+async def get_mass(
+    request: Request,
+    reader: Annotated[Reader, Depends(get_reader_dependency)],
+    active_tab: str = "create",
+) -> HTMLResponse:
+    """Mass operations page: create, delete, or modify feeds in bulk.
+
+    Args:
+        request: The request object.
+        reader: The Reader instance.
+        active_tab: The active tab (create, delete, modify).
+
+    Returns:
+        HTMLResponse: The mass operations page.
+    """
+    hooks: list[dict[str, str]] = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+
+    context: dict[str, typing.Any] = {
+        "request": request,
+        "webhooks": hooks,
+        "all_feeds_grouped": _get_grouped_feeds(reader),
+        "active_tab": active_tab,
+    }
+    return templates.TemplateResponse(request=request, name="mass.html", context=context)
+
+
+def _create_and_tag_feed(reader: Reader, feed_url: str, webhook_url: str) -> str | None:
+    """Add a feed and set its tags, without updating.
+
+    Returns:
+        The feed URL on success, or None if adding failed.
+    """
+    clean_url: str = feed_url.strip()
+    try:
+        reader.add_feed(clean_url)
+    except FeedExistsError:
+        pass
+    except ReaderError:
+        return None
+
+    reader.set_tag(clean_url, "webhook", webhook_url)  # pyright: ignore[reportArgumentType]
+    reader.set_tag(clean_url, "save_sent_webhooks", True)  # pyright: ignore[reportArgumentType]
+    reader.set_tag(clean_url, "media_gallery_image_limit", cast("JSONType", 1))
+
+    global_webhook_text_length_limit: int = coerce_webhook_text_length_limit(
+        cast("JsonValue", reader.get_tag((), "webhook_text_length_limit", 4000)),  # pyright: ignore[reportArgumentType]
+    )
+    reader.set_tag(clean_url, "webhook_text_length_limit", cast("JSONType", global_webhook_text_length_limit))
+    reader.set_tag(clean_url, "custom_message", default_custom_message)  # pyright: ignore[reportArgumentType]
+
+    global_screenshot_layout: str = str(reader.get_tag((), "screenshot_layout", "desktop")).strip().lower()
+    if global_screenshot_layout not in {"desktop", "mobile"}:
+        global_screenshot_layout = "desktop"
+    reader.set_tag(clean_url, "screenshot_layout", global_screenshot_layout)  # pyright: ignore[reportArgumentType]
+
+    global_delivery_mode: str = str(reader.get_tag((), "delivery_mode", "embed")).strip().lower()
+    if global_delivery_mode not in {"embed", "text"}:
+        global_delivery_mode = "embed"
+    reader.set_tag(clean_url, "delivery_mode", global_delivery_mode)  # pyright: ignore[reportArgumentType]
+    reader.set_tag(clean_url, "should_send_embed", global_delivery_mode == "embed")  # pyright: ignore[reportArgumentType]
+    reader.set_tag(clean_url, "embed", json.dumps(default_custom_embed))  # pyright: ignore[reportArgumentType]
+
+    return clean_url
+
+
+def _modify_single_feed(  # ruff:ignore[complex-structure, too-many-branches, too-many-statements]
+    reader: Reader,
+    url: str,
+    modify_action: str,
+    modify_value: str,
+) -> dict[str, typing.Any]:
+    """Apply a modification action to a single feed and return the result.
+
+    Args:
+        reader: The Reader instance.
+        url: The feed URL to modify.
+        modify_action: The action to perform.
+        modify_value: The value for the action.
+
+    Returns:
+        dict: Result with url, success, error, and action_taken keys.
+    """
+    result: dict[str, typing.Any] = {
+        "url": url,
+        "success": False,
+        "error": "",
+        "action_taken": "",
+    }
+
+    try:
+        reader.get_feed(url)
+    except FeedNotFoundError:
+        result["error"] = "Feed not found"
+        return result
+
+    if modify_action == "pause":
+        reader.disable_feed_updates(url)
+        result["success"] = True
+        result["action_taken"] = "Paused"
+    elif modify_action == "unpause":
+        reader.enable_feed_updates(url)
+        result["success"] = True
+        result["action_taken"] = "Unpaused"
+    elif modify_action == "change_webhook":
+        webhooks: list[dict[str, str]] = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+        webhook_url: str = ""
+        for hook in webhooks:
+            if hook["name"] == modify_value:
+                webhook_url = hook["url"]
+                break
+        if webhook_url:
+            reader.set_tag(url, "webhook", webhook_url)  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = f"Webhook changed to {modify_value}"
+        else:
+            result["error"] = f"Webhook '{modify_value}' not found"
+    elif modify_action == "delivery_mode":
+        if modify_value == "embed":
+            reader.set_tag(url, "delivery_mode", "embed")  # pyright: ignore[reportArgumentType]
+            reader.set_tag(url, "should_send_embed", True)  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = "Delivery mode set to embed"
+        elif modify_value == "text":
+            reader.set_tag(url, "delivery_mode", "text")  # pyright: ignore[reportArgumentType]
+            reader.set_tag(url, "should_send_embed", False)  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = "Delivery mode set to text"
+        elif modify_value == "screenshot_desktop":
+            reader.set_tag(url, "delivery_mode", "screenshot")  # pyright: ignore[reportArgumentType]
+            reader.set_tag(url, "screenshot_layout", "desktop")  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = "Delivery mode set to screenshot (desktop)"
+        elif modify_value == "screenshot_mobile":
+            reader.set_tag(url, "delivery_mode", "screenshot")  # pyright: ignore[reportArgumentType]
+            reader.set_tag(url, "screenshot_layout", "mobile")  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = "Delivery mode set to screenshot (mobile)"
+        else:
+            result["error"] = f"Unknown delivery mode: {modify_value}"
+    elif modify_action == "screenshot_layout":
+        if modify_value in {"desktop", "mobile"}:
+            reader.set_tag(url, "screenshot_layout", modify_value)  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = f"Screenshot layout set to {modify_value}"
+        else:
+            result["error"] = f"Unknown layout: {modify_value}"
+    elif modify_action == "update_interval":
+        try:
+            interval: int = int(modify_value)
+        except ValueError as e:
+            result["error"] = str(e)
+            return result
+        if interval < 1:
+            result["error"] = "Interval must be at least 1 minute"
+        else:
+            reader.set_tag(url, ".reader.update", {"interval": interval})  # pyright: ignore[reportArgumentType]
+            result["success"] = True
+            result["action_taken"] = f"Update interval set to {interval} minute(s)"  # ruff:ignore[hardcoded-sql-expression]
+    else:
+        result["error"] = f"Unknown action: {modify_action}"
+
+    return result
+
+
+def _update_and_mark_read(db_path: Path, feed_url: str) -> tuple[str, bool, str]:
+    """Update a feed and mark entries as read, in its own reader instance.
+
+    Called from worker threads to parallelize HTTP fetches.
+
+    Returns:
+        (feed_url, success, error_message)
+    """
+    worker_reader: Reader = make_app_reader(db_path)
+    try:
+        worker_reader.update_feed(feed_url)
+        for entry in worker_reader.get_entries(feed=feed_url, read=False):
+            worker_reader.set_entry_read(entry, True)
+    except ReaderError as e:
+        logger.warning("Failed to update feed %s: %s", feed_url, e)
+        return feed_url, False, str(e)[:200]
+    except Exception as e:
+        logger.exception("Unexpected error updating feed %s", feed_url)
+        return feed_url, False, str(e)[:200]
+    finally:
+        worker_reader.close()
+    return feed_url, True, ""
+
+
+@app.post("/mass/create", response_class=HTMLResponse)
+async def post_mass_create(  # ruff:ignore[complex-structure]
+    request: Request,
+    feed_urls: Annotated[str, Form()],
+    webhook_dropdown: Annotated[str, Form()],
+    reader: Annotated[Reader, Depends(get_reader_dependency)],
+) -> HTMLResponse:
+    """Create multiple feeds at once.
+
+    Phase 1: Add feeds and set tags (sequential, fast, no HTTP).
+    Phase 2: Update feeds in parallel via a thread pool.
+
+    Args:
+        request: The request object.
+        feed_urls: Feed URLs (one per line).
+        webhook_dropdown: The webhook to attach feeds to.
+        reader: The Reader instance.
+
+    Returns:
+        HTMLResponse: The mass operations page with results.
+
+    Raises:
+        HTTPException: If the selected webhook is not found.
+    """
+    urls: list[str] = [url.strip() for url in feed_urls.strip().split("\n") if url.strip()]
+    results: list[dict[str, typing.Any]] = []
+
+    webhooks: list[dict[str, str]] = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+
+    # Resolve webhook name to URL once for all feeds
+    webhook_url: str = ""
+    for hook in webhooks:
+        if hook["name"] == webhook_dropdown:
+            webhook_url = hook["url"]
+            break
+
+    if not webhook_url:
+        raise HTTPException(status_code=404, detail="Webhook not found")
+
+    # Phase 1: Add feeds and set tags (sequential, fast)
+    urls_to_update: list[str] = []
+    for url in urls:
+        added_url: str | None = _create_and_tag_feed(reader, url, webhook_url)
+        if added_url:
+            urls_to_update.append(added_url)
+            results.append({"url": url, "success": False, "feed_url": None, "error": ""})
+            continue
+        results.append({"url": url, "success": False, "feed_url": None, "error": "Failed to add feed"})
+
+    # Phase 2: Update feeds in parallel
+    if urls_to_update:
+        db_path: Path = Path(data_dir) / "db.sqlite"
+        max_workers: int = min(10, len(urls_to_update))
+        with concurrent.futures.ThreadPoolExecutor(max_workers=max_workers) as executor:
+            future_to_url = {executor.submit(_update_and_mark_read, db_path, u): u for u in urls_to_update}
+            for future in concurrent.futures.as_completed(future_to_url):
+                original_url: str = future_to_url[future]
+                feed_url, update_success, error_msg = future.result()
+                # Find and update the matching result entry
+                for result in results:
+                    if result["url"] == original_url:
+                        result["success"] = update_success
+                        result["feed_url"] = feed_url if update_success else None
+                        result["error"] = error_msg
+                        break
+
+        reader.update_search()
+
+    success_count: int = sum(1 for r in results if r["success"])
+    if success_count > 0:
+        commit_state_change(reader, f"Mass create {success_count} feed(s)")
+
+    context: dict[str, typing.Any] = {
+        "request": request,
+        "webhooks": webhooks,
+        "all_feeds_grouped": _get_grouped_feeds(reader),
+        "active_tab": "create",
+        "feed_urls": feed_urls,
+        "selected_webhook": webhook_dropdown,
+        "create_results": results,
+        "message": f"Created {success_count} of {len(results)} feed(s).",
+    }
+    return templates.TemplateResponse(request=request, name="mass.html", context=context)
+
+
+@app.post("/mass/delete", response_class=HTMLResponse)
+async def post_mass_delete(
+    request: Request,
+    reader: Annotated[Reader, Depends(get_reader_dependency)],
+    feed_urls: Annotated[list[str] | None, Form()] = None,
+) -> HTMLResponse:
+    """Delete multiple feeds at once.
+
+    Args:
+        request: The request object.
+        reader: The Reader instance.
+        feed_urls: List of feed URLs to delete.
+
+    Returns:
+        HTMLResponse: The mass operations page with results.
+    """
+    if feed_urls is None:
+        feed_urls = []
+    results: list[dict[str, typing.Any]] = []
+
+    for url in feed_urls:
+        result: dict[str, typing.Any] = {"url": url, "success": False, "error": ""}
+        try:
+            reader.delete_feed(url)
+            result["success"] = True
+        except FeedNotFoundError:
+            result["error"] = "Feed not found"
+        except Exception as e:  # ruff:ignore[blind-except]
+            result["error"] = str(e)[:200]
+        results.append(result)
+
+    deleted_count: int = sum(1 for r in results if r["success"])
+    if deleted_count > 0:
+        commit_state_change(reader, f"Mass delete {deleted_count} feed(s)")
+
+    webhooks: list[dict[str, str]] = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+
+    failed_count: int = len(results) - deleted_count
+    context: dict[str, typing.Any] = {
+        "request": request,
+        "webhooks": webhooks,
+        "all_feeds_grouped": _get_grouped_feeds(reader),
+        "active_tab": "delete",
+        "delete_results": results,
+        "delete_summary": {"deleted": deleted_count, "failed": failed_count},
+        "message": f"Deleted {deleted_count} feed(s). {failed_count} failed.",
+    }
+    return templates.TemplateResponse(request=request, name="mass.html", context=context)
+
+
+@app.post("/mass/modify", response_class=HTMLResponse)
+async def post_mass_modify(
+    request: Request,
+    reader: Annotated[Reader, Depends(get_reader_dependency)],
+    feed_urls: Annotated[list[str] | None, Form()] = None,
+    modify_action: Annotated[str, Form()] = "",
+    modify_value: Annotated[str, Form()] = "",
+) -> HTMLResponse:
+    """Modify multiple feeds at once.
+
+    Args:
+        request: The request object.
+        reader: The Reader instance.
+        feed_urls: List of feed URLs to modify.
+        modify_action: The action to perform (pause, unpause, change_webhook, etc.).
+        modify_value: The value for the action.
+
+    Returns:
+        HTMLResponse: The mass operations page with results.
+    """
+    feed_urls_list: list[str] = feed_urls if feed_urls is not None else []
+    results: list[dict[str, typing.Any]] = []
+
+    for url in feed_urls_list:
+        try:
+            result = _modify_single_feed(reader, url, modify_action, modify_value)
+        except Exception as e:
+            logger.exception("Failed to modify feed %s", url)
+            result = {"url": url, "success": False, "error": str(e)[:200], "action_taken": ""}
+        results.append(result)
+
+    modified_count: int = sum(1 for r in results if r["success"])
+    failed_count: int = sum(1 for r in results if not r["success"])
+    if modified_count > 0:
+        commit_state_change(reader, f"Mass modify {modified_count} feed(s)")
+
+    webhooks = cast("list[dict[str, str]]", list(reader.get_tag((), "webhooks", [])))
+
+    context: dict[str, typing.Any] = {
+        "request": request,
+        "webhooks": webhooks,
+        "all_feeds_grouped": _get_grouped_feeds(reader),
+        "active_tab": "modify",
+        "modify_results": results,
+        "modify_action": modify_action,
+        "modify_value": modify_value,
+        "modify_summary": {
+            "modified": modified_count,
+            "failed": failed_count,
+            "skipped": 0,
+        },
+        "message": f"Modified {modified_count} feed(s). {failed_count} failed.",
+    }
+    return templates.TemplateResponse(request=request, name="mass.html", context=context)
+
+
 @app.get("/search", response_class=HTMLResponse)
 async def search(
     request: Request,
     query: str,
     reader: Annotated[Reader, Depends(get_reader_dependency)],
-):
+) -> HTMLResponse:
     """Get entries matching a full-text search query.
 
     Args:
diff --git a/discord_rss_bot/templates/mass.html b/discord_rss_bot/templates/mass.html
new file mode 100644
index 0000000..88a6af8
--- /dev/null
+++ b/discord_rss_bot/templates/mass.html
@@ -0,0 +1,355 @@
+{% extends "base.html" %}
+{% block title %}
+    Mass operations | discord-rss-bot
+{% endblock title %}
+{% block description %}
+    Mass create, delete, or modify RSS feeds in bulk.
+{% endblock description %}
+{% block content %}
+    {% if message %}
+        <div class="alert alert-info alert-dismissible fade show" role="alert">
+            <pre>{{ message }}</pre>
+            <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
+        </div>
+    {% endif %}
+    <ul class="nav nav-tabs nav-dark border-dark mb-3" id="massTabs" role="tablist">
+        <li class="nav-item" role="presentation">
+            <button class="nav-link text-muted {% if active_tab == 'create' %}active bg-dark text-light{% endif %}"
+                    id="create-tab"
+                    data-bs-toggle="tab"
+                    data-bs-target="#create"
+                    type="button"
+                    role="tab"
+                    aria-controls="create"
+                    aria-selected="{% if active_tab == 'create' %}true{% else %}false{% endif %}">
+                Mass Create
+            </button>
+        </li>
+        <li class="nav-item" role="presentation">
+            <button class="nav-link text-muted {% if active_tab == 'delete' %}active bg-dark text-light{% endif %}"
+                    id="delete-tab"
+                    data-bs-toggle="tab"
+                    data-bs-target="#delete"
+                    type="button"
+                    role="tab"
+                    aria-controls="delete"
+                    aria-selected="{% if active_tab == 'delete' %}true{% else %}false{% endif %}">
+                Mass Delete
+            </button>
+        </li>
+        <li class="nav-item" role="presentation">
+            <button class="nav-link text-muted {% if active_tab == 'modify' %}active bg-dark text-light{% endif %}"
+                    id="modify-tab"
+                    data-bs-toggle="tab"
+                    data-bs-target="#modify"
+                    type="button"
+                    role="tab"
+                    aria-controls="modify"
+                    aria-selected="{% if active_tab == 'modify' %}true{% else %}false{% endif %}">
+                Mass Modify
+            </button>
+        </li>
+    </ul>
+    <div class="tab-content" id="massTabsContent">
+        {# ===== Mass Create ===== #}
+        <div class="tab-pane fade {% if active_tab == 'create' %}show active{% endif %}"
+             id="create"
+             role="tabpanel"
+             aria-labelledby="create-tab">
+            <div class="card border border-dark p-3 text-light">
+                <h3 class="h5">Create multiple feeds</h3>
+                <p class="text-muted small mb-3">Enter one feed URL per line. All feeds will be attached to the selected webhook.</p>
+                <form action="/mass/create" method="post">
+                    <div class="mb-3">
+                        <label for="feed_urls" class="form-label">Feed URLs (one per line)</label>
+                        <textarea name="feed_urls"
+                                  id="feed_urls"
+                                  class="form-control bg-dark border-dark text-muted"
+                                  rows="10"
+                                  placeholder="https://example.com/feed.xml&#10;https://other.com/rss&#10;https://third.com/atom">{{ feed_urls or '' }}</textarea>
+                    </div>
+                    <div class="mb-3">
+                        <label for="webhook_dropdown" class="form-label">Webhook</label>
+                        <select class="form-select bg-dark border-dark text-muted"
+                                id="webhook_dropdown"
+                                name="webhook_dropdown"
+                                required>
+                            <option value="" {% if not selected_webhook %}selected{% endif %} disabled>Choose webhook...</option>
+                            {% for hook in webhooks %}
+                                <option value="{{ hook.name }}"
+                                        {% if hook.name == selected_webhook %}selected{% endif %}>{{ hook.name }}</option>
+                            {% endfor %}
+                        </select>
+                    </div>
+                    <button type="submit" class="btn btn-primary">Create all feeds</button>
+                </form>
+            </div>
+            {% if create_results %}
+                <div class="card border border-dark p-3 text-light mt-3">
+                    <h3 class="h5">Results</h3>
+                    <ul class="list-unstyled mb-0">
+                        {% for result in create_results %}
+                            <li class="mb-2 {% if result.success %}text-success{% else %}text-danger{% endif %}">
+                                <strong>{{ result.url }}</strong>
+                                {% if result.success %}
+                                    &check; Added
+                                    {% if result.feed_url %}
+                                        - <a class="text-success" href="/feed?feed_url={{ result.feed_url|encode_url }}">View feed</a>
+                                    {% endif %}
+                                {% else %}
+                                    &cross; {{ result.error }}
+                                {% endif %}
+                            </li>
+                        {% endfor %}
+                    </ul>
+                </div>
+            {% endif %}
+        </div>
+        {# ===== Mass Delete ===== #}
+        <div class="tab-pane fade {% if active_tab == 'delete' %}show active{% endif %}"
+             id="delete"
+             role="tabpanel"
+             aria-labelledby="delete-tab">
+            <div class="card border border-dark p-3 text-light">
+                <h3 class="h5">Delete multiple feeds</h3>
+                <p class="text-muted small mb-3">Select feeds to delete. This action cannot be undone.</p>
+                {% if all_feeds_grouped %}
+                    <form id="mass-delete-form" action="/mass/delete" method="post">
+                        {% for group in all_feeds_grouped %}
+                            <div class="mb-3 border border-dark p-2">
+                                <div class="d-flex justify-content-between align-items-center mb-2">
+                                    <h4 class="h6 mb-0">{{ group.name }} ({{ group.feeds|length }})</h4>
+                                    <div>
+                                        <button type="button"
+                                                class="btn btn-outline-light btn-sm select-all"
+                                                data-group="{{ group.group_idx }}">Select all</button>
+                                        <button type="button"
+                                                class="btn btn-outline-secondary btn-sm deselect-all"
+                                                data-group="{{ group.group_idx }}">Deselect all</button>
+                                    </div>
+                                </div>
+                                <ul class="list-unstyled mb-0">
+                                    {% for item in group.feeds %}
+                                        {% set feed = item.feed %}
+                                        <li class="form-check">
+                                            <input class="form-check-input mass-delete-checkbox group-{{ group.group_idx }}"
+                                                   type="checkbox"
+                                                   name="feed_urls"
+                                                   value="{{ feed.url }}"
+                                                   id="delete-{{ group.group_idx }}-{{ item.feed_idx }}" />
+                                            <label class="form-check-label text-muted" for="delete-{{ group.group_idx }}-{{ item.feed_idx }}">
+                                                {% if feed.title %}
+                                                    {{ feed.title }}
+                                                {% else %}
+                                                    {{ feed.url }}
+                                                {% endif %}
+                                                {% if feed.title %}<span class="small">- {{ feed.url }}</span>{% endif %}
+                                                {% if not feed.updates_enabled %}<span class="text-warning small">Paused</span>{% endif %}
+                                                {% if feed.last_exception %}<span class="text-danger small">Error</span>{% endif %}
+                                            </label>
+                                        </li>
+                                    {% endfor %}
+                                </ul>
+                            </div>
+                        {% endfor %}
+                        <button type="submit"
+                                class="btn btn-danger"
+                                onclick="return confirm('Are you sure you want to delete the selected feeds? This cannot be undone.');">
+                            Delete selected feeds
+                        </button>
+                    </form>
+                {% else %}
+                    <p class="text-muted mb-0">No feeds found.</p>
+                {% endif %}
+            </div>
+            {% if delete_results %}
+                <div class="card border border-dark p-3 text-light mt-3">
+                    <h3 class="h5">Results</h3>
+                    <ul class="list-unstyled mb-0">
+                        {% for result in delete_results %}
+                            <li class="mb-2 {% if result.success %}text-success{% else %}text-danger{% endif %}">
+                                <strong>{{ result.url }}</strong>
+                                {% if result.success %}
+                                    &check; Deleted
+                                {% else %}
+                                    &cross; {{ result.error }}
+                                {% endif %}
+                            </li>
+                        {% endfor %}
+                        <li class="mt-2 text-muted">{{ delete_summary.deleted }} deleted, {{ delete_summary.failed }} failed</li>
+                    </ul>
+                </div>
+            {% endif %}
+        </div>
+        {# ===== Mass Modify ===== #}
+        <div class="tab-pane fade {% if active_tab == 'modify' %}show active{% endif %}"
+             id="modify"
+             role="tabpanel"
+             aria-labelledby="modify-tab">
+            <div class="card border border-dark p-3 text-light">
+                <h3 class="h5">Modify multiple feeds</h3>
+                <p class="text-muted small mb-3">Select feeds and choose a setting to update.</p>
+                {% if all_feeds_grouped %}
+                    <form id="mass-modify-form" action="/mass/modify" method="post">
+                        {% for group in all_feeds_grouped %}
+                            <div class="mb-3 border border-dark p-2">
+                                <div class="d-flex justify-content-between align-items-center mb-2">
+                                    <h4 class="h6 mb-0">{{ group.name }} ({{ group.feeds|length }})</h4>
+                                    <div>
+                                        <button type="button"
+                                                class="btn btn-outline-light btn-sm select-all"
+                                                data-group="modify-{{ group.group_idx }}">Select all</button>
+                                        <button type="button"
+                                                class="btn btn-outline-secondary btn-sm deselect-all"
+                                                data-group="modify-{{ group.group_idx }}">Deselect all</button>
+                                    </div>
+                                </div>
+                                <ul class="list-unstyled mb-0">
+                                    {% for item in group.feeds %}
+                                        {% set feed = item.feed %}
+                                        <li class="form-check">
+                                            <input class="form-check-input mass-modify-checkbox group-modify-{{ group.group_idx }}"
+                                                   type="checkbox"
+                                                   name="feed_urls"
+                                                   value="{{ feed.url }}"
+                                                   id="modify-{{ group.group_idx }}-{{ item.feed_idx }}" />
+                                            <label class="form-check-label text-muted"
+                                                   for="modify-{{ group.group_idx }}-{{ item.feed_idx }}">
+                                                {% if feed.title %}
+                                                    {{ feed.title }}
+                                                {% else %}
+                                                    {{ feed.url }}
+                                                {% endif %}
+                                                {% if feed.title %}<span class="small">- {{ feed.url }}</span>{% endif %}
+                                                {% if not feed.updates_enabled %}<span class="text-warning small">Paused</span>{% endif %}
+                                            </label>
+                                        </li>
+                                    {% endfor %}
+                                </ul>
+                            </div>
+                        {% endfor %}
+                        <hr class="border-secondary" />
+                        <div class="row g-3">
+                            <div class="col-md-4">
+                                <label for="modify_action" class="form-label">Action</label>
+                                <select class="form-select bg-dark border-dark text-muted"
+                                        id="modify_action"
+                                        name="modify_action"
+                                        required>
+                                    <option value="" disabled {% if not modify_action %}selected{% endif %}>Choose action...</option>
+                                    <option value="pause" {% if modify_action == 'pause' %}selected{% endif %}>Pause (disable updates)</option>
+                                    <option value="unpause" {% if modify_action == 'unpause' %}selected{% endif %}>Unpause (enable updates)</option>
+                                    <option value="change_webhook" {% if modify_action == 'change_webhook' %}selected{% endif %}>Change webhook</option>
+                                    <option value="delivery_mode" {% if modify_action == 'delivery_mode' %}selected{% endif %}>Change delivery mode</option>
+                                    <option value="screenshot_layout" {% if modify_action == 'screenshot_layout' %}selected{% endif %}>Change screenshot layout</option>
+                                    <option value="update_interval" {% if modify_action == 'update_interval' %}selected{% endif %}>Change update interval (minutes)</option>
+                                </select>
+                            </div>
+                            <div class="col-md-4" id="modify-value-group">
+                                <label for="modify_value" class="form-label">Value</label>
+                                <div id="modify-value-dynamic">
+                                    <input type="text"
+                                           name="modify_value"
+                                           id="modify_value"
+                                           class="form-control bg-dark border-dark text-muted"
+                                           value="{{ modify_value or '' }}"
+                                           placeholder="New value" />
+                                </div>
+                            </div>
+                        </div>
+                        <button type="submit" class="btn btn-warning mt-3">Apply to selected feeds</button>
+                    </form>
+                {% else %}
+                    <p class="text-muted mb-0">No feeds found.</p>
+                {% endif %}
+            </div>
+            {% if modify_results %}
+                <div class="card border border-dark p-3 text-light mt-3">
+                    <h3 class="h5">Results</h3>
+                    <ul class="list-unstyled mb-0">
+                        {% for result in modify_results %}
+                            <li class="mb-2 {% if result.success %}text-success{% else %}text-danger{% endif %}">
+                                <strong>{{ result.url }}</strong>
+                                {% if result.success %}
+                                    &check; {{ result.action_taken }}
+                                {% else %}
+                                    &cross; {{ result.error }}
+                                {% endif %}
+                            </li>
+                        {% endfor %}
+                        <li class="mt-2 text-muted">
+                            {{ modify_summary.modified }} modified, {{ modify_summary.failed }} failed, {{ modify_summary.skipped }} skipped
+                        </li>
+                    </ul>
+                </div>
+            {% endif %}
+        </div>
+    </div>
+{% endblock content %}
+{% block head %}
+    <script>
+        document.addEventListener('DOMContentLoaded', function() {
+            // Select/Deselect all for mass delete and modify checkboxes
+            document.querySelectorAll('.select-all').forEach(function(btn) {
+                btn.addEventListener('click', function() {
+                    var group = this.getAttribute('data-group');
+                    document.querySelectorAll('.group-' + group).forEach(function(cb) {
+                        cb.checked = true;
+                    });
+                });
+            });
+            document.querySelectorAll('.deselect-all').forEach(function(btn) {
+                btn.addEventListener('click', function() {
+                    var group = this.getAttribute('data-group');
+                    document.querySelectorAll('.group-' + group).forEach(function(cb) {
+                        cb.checked = false;
+                    });
+                });
+            });
+
+            // Dynamic value field for modify action
+            var actionSelect = document.getElementById('modify_action');
+            var valueDynamic = document.getElementById('modify-value-dynamic');
+            if (actionSelect && valueDynamic) {
+                function updateModifyValueField() {
+                    var action = actionSelect.value;
+                    var html = '';
+                    if (action === 'pause' || action === 'unpause') {
+                        html = '<p class="text-muted small mt-2">No additional value needed.</p>';
+                    } else if (action === 'change_webhook') {
+                        html = `<select name="modify_value" class="form-select bg-dark border-dark text-muted" required>
+                                    <option value="" disabled selected>Choose webhook...</option>
+                                    {% for hook in webhooks %}
+                                        <option value="{{ hook.name }}">{{ hook.name }}</option>
+                                    {% endfor %}
+                                </select>`;
+                    } else if (action === 'delivery_mode') {
+                        html = `<select name="modify_value" class="form-select bg-dark border-dark text-muted" required>
+                                    <option value="" disabled selected>Choose mode...</option>
+                                    <option value="embed">Embed</option>
+                                    <option value="text">Text</option>
+                                    <option value="screenshot_desktop">Screenshot (Desktop)</option>
+                                    <option value="screenshot_mobile">Screenshot (Mobile)</option>
+                                </select>`;
+                    } else if (action === 'screenshot_layout') {
+                        html = `<select name="modify_value" class="form-select bg-dark border-dark text-muted" required>
+                                    <option value="" disabled selected>Choose layout...</option>
+                                    <option value="desktop">Desktop</option>
+                                    <option value="mobile">Mobile</option>
+                                </select>`;
+                    } else if (action === 'update_interval') {
+                        html = '<input type="number" name="modify_value" class="form-control bg-dark border-dark text-muted" required min="1" value="15" placeholder="Minutes" />';
+                    } else {
+                        html = '<input type="text" name="modify_value" class="form-control bg-dark border-dark text-muted" placeholder="Value" />';
+                    }
+                    valueDynamic.innerHTML = html;
+                }
+                actionSelect.addEventListener('change', updateModifyValueField);
+                // Init
+                if (actionSelect.value) {
+                    updateModifyValueField();
+                }
+            }
+        });
+    </script>
+{% endblock head %}
diff --git a/discord_rss_bot/templates/nav.html b/discord_rss_bot/templates/nav.html
index 1fb1728..d0a5cdf 100644
--- a/discord_rss_bot/templates/nav.html
+++ b/discord_rss_bot/templates/nav.html
@@ -18,6 +18,10 @@
                     </li>
                     <li class="nav-item nav-link d-none d-md-block">|</li>
                 {% endif %}
+                <li class="nav-item">
+                    <a class="nav-link" href="/mass">Mass ops</a>
+                </li>
+                <li class="nav-item nav-link d-none d-md-block">|</li>
                 <li class="nav-item">
                     <a class="nav-link" href="/webhooks">Webhooks</a>
                 </li>
diff --git a/tests/test_main.py b/tests/test_main.py
index b69f06d..ee1b12a 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -14,8 +14,10 @@ from typing import cast
 from unittest.mock import MagicMock
 from unittest.mock import patch
 
+import pytest
 from fastapi.testclient import TestClient
 from reader import FeedExistsError
+from reader import FeedNotFoundError
 
 import discord_rss_bot.main as main_module
 from discord_rss_bot import feeds
@@ -26,7 +28,6 @@ from discord_rss_bot.main import get_reader_dependency
 if TYPE_CHECKING:
     from pathlib import Path
 
-    import pytest
     from httpx2 import Response
     from reader import Entry
     from reader import Reader
@@ -3355,3 +3356,532 @@ def test_post_set_custom_clears_username_and_avatar() -> None:
         assert not stub.set_tag.call_args_list[1].args[2]
     finally:
         app.dependency_overrides = {}
+
+
+# ---------------------------------------------------------------------------
+# Mass operations tests
+# ---------------------------------------------------------------------------
+
+
+class _StubFeedForMass:
+    """Minimal feed stub for mass operations tests."""
+
+    def __init__(self, url: str, title: str | None = None, updates_enabled: bool = True) -> None:  # ruff:ignore[boolean-default-value-positional-argument, boolean-type-hint-positional-argument]
+        self.url: str = url
+        self.title: str | None = title
+        self.updates_enabled: bool = updates_enabled
+        self.last_exception: str | None = None
+
+
+class _StubReaderForMass:
+    """Stub reader with feeds grouped under a webhook, used by mass operations tests."""
+
+    def __init__(
+        self,
+        feeds: list[_StubFeedForMass] | None = None,
+        *,
+        webhook_name: str = "",
+        webhook_url: str = "",
+        delete_fail: bool = False,
+    ) -> None:
+        self._feeds: list[_StubFeedForMass] = feeds or []
+        self._webhook_name: str = webhook_name
+        self._webhook_url: str = webhook_url
+        self._delete_fail: bool = delete_fail
+        self.set_tag_calls: list[tuple[str, str, object]] = []
+        self.disabled_feeds: set[str] = set()
+        self.enabled_feeds: set[str] = set()
+
+    def get_feeds(self) -> list[_StubFeedForMass]:
+        """Return the list of feeds."""
+        return self._feeds
+
+    def get_tag(self, resource: tuple[()] | str, key: str, default: TestTagValue = None) -> TestTagValue:  # ruff:ignore[too-many-return-statements]
+        """Return stored tag values."""
+        if resource == () and key == "webhooks":
+            if self._webhook_name:
+                return [{"name": self._webhook_name, "url": self._webhook_url}]
+            return []
+        if resource == () and key == "delivery_mode":
+            return "embed"
+        if resource == () and key == "webhook_text_length_limit":
+            return 4000
+        if resource == () and key == "screenshot_layout":
+            return "desktop"
+        if isinstance(resource, str) and key == "webhook":
+            return self._webhook_url
+        return default
+
+    def set_tag(self, resource: str, key: str, value: object) -> None:  # pyright: ignore[reportArgumentType]
+        """Record tag set calls."""
+        self.set_tag_calls.append((resource, key, value))
+
+    def update_search(self) -> None:
+        """No-op search index update."""
+
+    def delete_feed(self, url: str) -> None:
+        """Delete a feed by URL.
+
+        Raises:
+            RuntimeError: If delete_fail was set in the constructor.
+        """
+        if self._delete_fail:
+            msg = "Delete failed"
+            raise RuntimeError(msg)
+        self._feeds = [f for f in self._feeds if f.url != url]
+
+    def get_feed(self, url: str) -> _StubFeedForMass:
+        """Get a feed by URL.
+
+        Returns:
+            The matching feed.
+
+        Raises:
+            FeedNotFoundError: If no feed matches the URL.
+        """
+        for feed in self._feeds:
+            if feed.url == url:
+                return feed
+        raise FeedNotFoundError(url)
+
+    def disable_feed_updates(self, url: str) -> None:
+        """Disable updates for a feed."""
+        self.disabled_feeds.add(url)
+        self.enabled_feeds.discard(url)
+
+    def enable_feed_updates(self, url: str) -> None:
+        """Enable updates for a feed."""
+        self.enabled_feeds.add(url)
+        self.disabled_feeds.discard(url)
+
+    def add_feed(self, url: str) -> None:
+        """Add a feed to the stub."""
+        self._feeds.append(_StubFeedForMass(url=url))
+
+
+MASS_FEED_1_URL: str = "https://example.com/feed1.xml"
+MASS_FEED_2_URL: str = "https://example.com/feed2.xml"
+MASS_WEBHOOK_NAME: str = "Mass test webhook"
+MASS_WEBHOOK_URL: str = "https://discord.com/api/webhooks/mass/abc"
+
+
+@pytest.fixture
+def mass_stub_reader() -> _StubReaderForMass:
+    """Create a stub reader with feeds for mass operations tests.
+
+    Returns:
+        A configured stub reader instance.
+    """
+    return _StubReaderForMass(
+        feeds=[
+            _StubFeedForMass(url=MASS_FEED_1_URL, title="Feed One"),
+            _StubFeedForMass(url=MASS_FEED_2_URL, title="Feed Two", updates_enabled=False),
+        ],
+        webhook_name=MASS_WEBHOOK_NAME,
+        webhook_url=MASS_WEBHOOK_URL,
+    )
+
+
+class TestMassPage:
+    """Tests for the mass operations page."""
+
+    def test_mass_page_loads(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """GET /mass should render all three tabs."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.get("/mass")
+            assert response.status_code == 200
+            assert "Mass Create" in response.text
+            assert "Mass Delete" in response.text
+            assert "Mass Modify" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_mass_page_shows_feeds_when_webhook_exists(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """GET /mass should list feeds grouped by webhook."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.get("/mass")
+            assert response.status_code == 200
+            assert MASS_WEBHOOK_NAME in response.text
+            assert "Feed One" in response.text
+            assert "Feed Two" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_mass_page_no_feeds_shows_empty_state(self) -> None:
+        """GET /mass with no feeds should show 'No feeds found'."""
+        stub = _StubReaderForMass(webhook_name=MASS_WEBHOOK_NAME, webhook_url=MASS_WEBHOOK_URL)
+        app.dependency_overrides[get_reader_dependency] = lambda: stub
+        try:
+            response: Response = client.get("/mass")
+            assert response.status_code == 200
+            assert "No feeds found" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_mass_page_defaults_to_create_tab(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """GET /mass without active_tab should default to create tab."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.get("/mass")
+            assert response.status_code == 200
+            assert 'id="create-tab"' in response.text
+            assert 'aria-selected="true"' in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_mass_page_respects_active_tab_param(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """GET /mass?active_tab=delete should show delete tab active."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.get("/mass?active_tab=delete")
+            assert response.status_code == 200
+            assert "Delete multiple feeds" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_mass_page_shows_webhooks_in_create_form(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """The mass create tab should list webhooks in the dropdown."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.get("/mass")
+            assert response.status_code == 200
+            assert MASS_WEBHOOK_NAME in response.text
+            assert "Create all feeds" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+
+class TestMassDelete:
+    """Tests for POST /mass/delete."""
+
+    def test_delete_selected_feeds(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/delete with feed URLs should delete them."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/delete",
+                    data={"feed_urls": [MASS_FEED_1_URL, MASS_FEED_2_URL]},
+                )
+            assert response.status_code == 200
+            assert "Deleted 2 feed(s)" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_delete_no_selection(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/delete with no feed URLs should not crash."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post("/mass/delete")
+            assert response.status_code == 200
+            assert "Deleted 0 feed(s)" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_delete_feed_error_does_not_crash(self) -> None:
+        """POST /mass/delete should handle reader errors gracefully."""
+        stub = _StubReaderForMass(
+            feeds=[_StubFeedForMass(url=MASS_FEED_1_URL)],
+            delete_fail=True,
+        )
+        app.dependency_overrides[get_reader_dependency] = lambda: stub
+        try:
+            response: Response = client.post("/mass/delete", data={"feed_urls": [MASS_FEED_1_URL]})
+            assert response.status_code == 200
+            assert "0 deleted, 1 failed" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+
+class TestMassModify:
+    """Tests for POST /mass/modify."""
+
+    def test_modify_pause_feed(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with pause action should disable feed updates."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_1_URL],
+                        "modify_action": "pause",
+                        "modify_value": "",
+                    },
+                )
+            assert response.status_code == 200
+            assert MASS_FEED_1_URL in response.text
+            assert "Modified 1 feed(s)" in response.text
+            assert MASS_FEED_1_URL in mass_stub_reader.disabled_feeds
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_unpause_feed(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with unpause action should enable feed updates."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_2_URL],
+                        "modify_action": "unpause",
+                        "modify_value": "",
+                    },
+                )
+            assert response.status_code == 200
+            assert "Modified 1 feed(s)" in response.text
+            assert MASS_FEED_2_URL in mass_stub_reader.enabled_feeds
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_nonexistent_feed(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify for a non-existent feed should report error."""
+        nonexistent = "https://example.com/nonexistent.xml"
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post(
+                "/mass/modify",
+                data={
+                    "feed_urls": [nonexistent],
+                    "modify_action": "pause",
+                    "modify_value": "",
+                },
+            )
+            assert response.status_code == 200
+            assert "0 modified, 1 failed" in response.text
+            assert "Feed not found" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_unknown_action(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with an unknown action should report error."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post(
+                "/mass/modify",
+                data={
+                    "feed_urls": [MASS_FEED_1_URL],
+                    "modify_action": "nonexistent_action",
+                    "modify_value": "",
+                },
+            )
+            assert response.status_code == 200
+            assert "0 modified, 1 failed" in response.text
+            assert "Unknown action" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_change_webhook_updates_tag(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with change_webhook should call set_tag with the new webhook URL."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_1_URL],
+                        "modify_action": "change_webhook",
+                        "modify_value": MASS_WEBHOOK_NAME,
+                    },
+                )
+            assert response.status_code == 200
+            assert "Modified 1 feed(s)" in response.text
+            # Check that set_tag was called with the webhook tag
+            webhook_calls = [c for c in mass_stub_reader.set_tag_calls if c[1] == "webhook"]
+            assert len(webhook_calls) == 1
+            assert webhook_calls[0][2] == MASS_WEBHOOK_URL
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_unknown_webhook_reports_error(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with a non-existent webhook name should report error."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post(
+                "/mass/modify",
+                data={
+                    "feed_urls": [MASS_FEED_1_URL],
+                    "modify_action": "change_webhook",
+                    "modify_value": "Nonexistent Hook",
+                },
+            )
+            assert response.status_code == 200
+            assert "0 modified, 1 failed" in response.text
+            assert "not found" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_delivery_mode_embed(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with delivery_mode=embed should set delivery_mode and should_send_embed."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_1_URL],
+                        "modify_action": "delivery_mode",
+                        "modify_value": "embed",
+                    },
+                )
+            assert response.status_code == 200
+            assert "Modified 1 feed(s)" in response.text
+            delivery_calls = [c for c in mass_stub_reader.set_tag_calls if c[1] == "delivery_mode"]
+            embed_calls = [c for c in mass_stub_reader.set_tag_calls if c[1] == "should_send_embed"]
+            assert len(delivery_calls) == 1
+            assert delivery_calls[0][2] == "embed"
+            assert len(embed_calls) == 1
+            assert embed_calls[0][2] is True
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_delivery_mode_text(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with delivery_mode=text should set should_send_embed to False."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_1_URL],
+                        "modify_action": "delivery_mode",
+                        "modify_value": "text",
+                    },
+                )
+            assert response.status_code == 200
+            assert "Modified 1 feed(s)" in response.text
+            embed_calls = [c for c in mass_stub_reader.set_tag_calls if c[1] == "should_send_embed"]
+            assert len(embed_calls) == 1
+            assert embed_calls[0][2] is False
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_update_interval(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with update_interval should store the interval."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            with patch("discord_rss_bot.main.commit_state_change"):
+                response: Response = client.post(
+                    "/mass/modify",
+                    data={
+                        "feed_urls": [MASS_FEED_1_URL],
+                        "modify_action": "update_interval",
+                        "modify_value": "30",
+                    },
+                )
+            assert response.status_code == 200
+            assert "Modified 1 feed(s)" in response.text
+            update_calls = [c for c in mass_stub_reader.set_tag_calls if c[1] == ".reader.update"]
+            assert len(update_calls) == 1
+            assert update_calls[0][2] == {"interval": 30}
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_update_interval_invalid(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with non-numeric update_interval should report error."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post(
+                "/mass/modify",
+                data={
+                    "feed_urls": [MASS_FEED_1_URL],
+                    "modify_action": "update_interval",
+                    "modify_value": "not-a-number",
+                },
+            )
+            assert response.status_code == 200
+            assert "0 modified, 1 failed" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_modify_no_selection(self, mass_stub_reader: _StubReaderForMass) -> None:
+        """POST /mass/modify with no feed URLs should not crash."""
+        app.dependency_overrides[get_reader_dependency] = lambda: mass_stub_reader
+        try:
+            response: Response = client.post(
+                "/mass/modify",
+                data={"modify_action": "pause", "modify_value": ""},
+            )
+            assert response.status_code == 200
+            assert "Modified 0 feed(s)" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+
+class TestMassCreate:
+    """Tests for POST /mass/create."""
+
+    def test_create_rejects_missing_webhook(self) -> None:
+        """POST /mass/create without a valid webhook should return 404."""
+        stub = _StubReaderForMass()
+        app.dependency_overrides[get_reader_dependency] = lambda: stub
+        try:
+            response: Response = client.post(
+                "/mass/create",
+                data={
+                    "feed_urls": "https://example.com/feed.xml",
+                    "webhook_dropdown": "nonexistent",
+                },
+            )
+            assert response.status_code == 404
+            assert "Webhook not found" in response.text
+        finally:
+            app.dependency_overrides = {}
+
+    def test_create_single_url(self) -> None:
+        """POST /mass/create with a single URL should attempt to create it."""
+        stub = _StubReaderForMass(webhook_name=MASS_WEBHOOK_NAME, webhook_url=MASS_WEBHOOK_URL)
+        app.dependency_overrides[get_reader_dependency] = lambda: stub
+        try:
+            with (
+                patch("discord_rss_bot.main._update_and_mark_read") as mock_update,
+                patch("discord_rss_bot.main.commit_state_change"),
+            ):
+                mock_update.return_value = ("https://example.com/new-feed.xml", True, "")
+                response: Response = client.post(
+                    "/mass/create",
+                    data={
+                        "feed_urls": "https://example.com/new-feed.xml",
+                        "webhook_dropdown": MASS_WEBHOOK_NAME,
+                    },
+                )
+            assert response.status_code == 200
+        finally:
+            app.dependency_overrides = {}
+
+    def test_create_multiple_urls(self) -> None:
+        """POST /mass/create with multiple URLs should attempt to create them."""
+        stub = _StubReaderForMass(webhook_name=MASS_WEBHOOK_NAME, webhook_url=MASS_WEBHOOK_URL)
+        app.dependency_overrides[get_reader_dependency] = lambda: stub
+        try:
+            with (
+                patch("discord_rss_bot.main._update_and_mark_read") as mock_update,
+                patch("discord_rss_bot.main.commit_state_change"),
+            ):
+                mock_update.side_effect = [
+                    ("https://example.com/feed1.xml", True, ""),
+                    ("https://example.com/feed2.xml", True, ""),
+                ]
+                response: Response = client.post(
+                    "/mass/create",
+                    data={
+                        "feed_urls": "https://example.com/feed1.xml\nhttps://example.com/feed2.xml",
+                        "webhook_dropdown": MASS_WEBHOOK_NAME,
+                    },
+                )
+            assert response.status_code == 200
+        finally:
+            app.dependency_overrides = {}
+
+
+class TestMassNav:
+    """Tests for the mass operations navigation link."""
+
+    def test_mass_link_in_navbar(self) -> None:
+        """The navbar should contain a link to the mass operations page."""
+        response: Response = client.get("/")
+        assert response.status_code == 200
+        assert "/mass" in response.text, f"Expected /mass link in navbar: {response.text}"