Jellyfin Missing Seasons Plugin

A Jellyfin plugin that displays missing seasons in your library as grayed-out, non-interactive indicators using TMDB metadata. Instantly see which seasons you're missing for any series.

Features

• Missing season detection — Scans TMDB data to find seasons you don't have in your library
• Grayed-out display — Missing seasons appear with grayscale filter and "Not available" badge
• Upcoming seasons — Future seasons already listed on TMDB appear with an "Upcoming" badge and their release date shown at the bottom-left of the card
• Episode count badge — Shows the number of episodes in each missing season (using Jellyfin's native badge styling)
• TMDB artwork — Displays official poster art from The Movie Database
• Adaptable display order — Configure whether missing seasons are interleaved in their natural position or grouped after all available seasons (via plugin settings page)
• Correct ordering — Inserts missing seasons in chronological order among existing seasons
• Non-interactive — Missing season cards are unclickable and can't be played

Requirements

• Jellyfin 10.8+
• Series must have TMDB metadata (automatic with default metadata providers)
• FileTransformation plugin installed on server (for v1.0.2+)

Installation

Step 1: Add the Repository

1. Open Jellyfin Dashboard → Plugins → Repositories
2. Click + Add Repository
3. Enter this URL:

   https://raw.githubusercontent.com/richardwerkman/jellyfin-plugins/main/manifest.json
   

4. Click Save

Step 2: Install the Plugin

1. Go to Plugins → Catalog
2. Find Missing Seasons and click it
3. Click Install
4. Jellyfin will download and extract the plugin

Step 3: Restart Jellyfin

1. Go to Dashboard → Settings (top right) → Restart
2. Wait for the server to restart (30-60 seconds)
3. Jellyfin will register the plugin with the FileTransformation service

Step 4: Hard-Refresh Your Browser

After restart, do a hard refresh to clear the cached index.html:

• Windows/Linux: Ctrl+Shift+R
• macOS: Cmd+Shift+R

How It Works

1. Detection — Plugin loads when you navigate to a series detail page
2. Metadata lookup — Reads the TMDB ID from Jellyfin's series metadata
3. TMDB query — Fetches season data from The Movie Database API
4. Comparison — Compares TMDB seasons against your Jellyfin library
5. Injection — Creates missing season cards with TMDB artwork and inserts them in correct order
6. Styling — Uses Jellyfin's native countIndicator and indicator classes for episode badge (matching your theme)

Architecture

• Client-side JS (missing-seasons.js) — Handles DOM manipulation, TMDB API calls, and card injection
• C# Plugin (Jellyfin.Plugin.MissingSeasons) — Serves the JS and manages FileTransformation integration
• FileTransformation Plugin — Dynamically injects the script tag into index.html at request time
• Cache-busting middleware — Strips conditional request headers to prevent 304 responses, ensuring the injected script is always delivered

Uninstallation

1. Go to Dashboard → Plugins
2. Click the ⚙️ gear icon next to Missing Seasons
3. Click Uninstall
4. Restart Jellyfin

Troubleshooting

Problem	Solution
No missing seasons appear	Check browser console (F12) for [MissingSeasons] log messages. Verify the series has TMDB metadata.
Script tag not in index.html	Ensure FileTransformation plugin is installed. Check Jellyfin logs for plugin startup errors.
Missing seasons appear but disappear on reload	Hard-refresh your browser (Ctrl+Shift+R) to clear cached index.html.
Wrong styling/colors	Hard-refresh browser. Missing seasons use Jellyfin's native indicator classes, so styling should match your theme automatically.
CORS errors in console	Verify you can access https://api.themoviedb.org from your network. Public TMDB API should be accessible.
Plugin says "Active" but nothing appears	Restart Jellyfin. FileTransformation plugin must fully initialize before the service is available.

Browser Support

• ✅ Chrome / Chromium (latest)
• ✅ Firefox (latest)
• ✅ Safari (latest)
• ✅ Edge (latest)

Performance Notes

• Minimal overhead — Only activated on series detail pages
• Network — One TMDB API call per series (cached in memory during session)
• Rendering — Card injection happens once when the seasons section loads
• MutationObserver — Watches for dynamic content changes, with debouncing to prevent excessive re-renders

Contributing

Issues, suggestions, and pull requests are welcome! Please open an issue on GitHub.

License

MIT

Credits

• Jellyfin — Open-source media system
• TMDB — Movie and TV data
• FileTransformation Plugin — Dynamic script injection