The Stream Detector: Find and Copy Stream URLs in Firefox
The Stream Detector is a free, open source browser extension for Firefox that lists the streaming playlists and subtitle files a web page loads, such as M3U8 (HLS) and MPD (MPEG-DASH) manifests. Click its toolbar icon, pick a detected stream, and it copies the URL or a ready-made command for yt-dlp, FFmpeg or Streamlink, so you can play, record or archive the stream in another program.
This guide covers what the add-on detects, how to use it, the Firefox and Chrome versions, the permissions it asks for, and where it stops working.
What does The Stream Detector do?
The Stream Detector watches the network requests of open tabs and records the stream manifests and subtitle tracks that video and audio players request. Most web players do not load one video file; they load a playlist that points to many small segments. The add-on catches that playlist URL, which is the address external players and recorders need.
According to its Mozilla Add-ons listing, it tracks playlists and subtitles used by four streaming technologies: Apple HLS, Adobe HDS, MPEG-DASH and Microsoft Smooth Streaming. It can also download plain video and audio files directly and monitor additional file extensions and Content-Type headers that you define.
The add-on is published by the developer 54ac under the Mozilla Public License 2.0, and its source code is on GitHub. It does not download or convert streams itself: it hands the URL to the tool of your choice.
How to use The Stream Detector in Firefox
Using The Stream Detector takes a few clicks once the add-on is installed:
- Install The Stream Detector from addons.mozilla.org and pin its icon to the Firefox toolbar.
- Open the page with the stream and start playback, so the player requests its playlist.
- Watch the toolbar icon: a badge shows how many streams were detected.
- Click the icon and click a stream's filename to copy its URL to the clipboard.
- To copy a command instead, switch the copy format in the popup to the tool you use, then click the filename.
- Paste the URL into a player such as VLC, or paste the command into a terminal.
The popup includes a filter field to find a specific stream when a page loads many, and an option to copy all URLs at once. Version 2.11 added a sidebar view, which keeps the list of detected streams visible while you browse.
Supported stream formats and tools
The Stream Detector supports four adaptive streaming formats and copies commands for five download and playback tools. The table summarizes what it recognizes and what it can produce.
| Item | Covered by The Stream Detector |
|---|---|
| Playlist formats | M3U8 (Apple HLS), F4M (Adobe HDS), MPD (MPEG-DASH), ISM (Microsoft Smooth Streaming) |
| Subtitle formats | VTT, SRT, TTML, TTML2, DFXP |
| Command formats | yt-dlp (recommended by the developer), FFmpeg, Streamlink, hlsdl, N_m3u8DL |
| Headers in commands | User-Agent, Cookie and Referer, so the tool requests the stream like the browser did |
Including the headers matters: many servers refuse playlist requests without the right Referer or session cookie. Since version 2.11.7, the add-on can also tell yt-dlp to read cookies from the browser when it detects none on the request.
Options and customization
The options page of The Stream Detector controls what the add-on monitors and what a click on a stream does. The most useful settings change the default click action from copying the plain URL to copying a command for your preferred tool, and enable direct downloads of media files.
You can add your own file extensions and Content-Type headers to detect, which helps when a site uses an uncommon manifest type. The options screenshot above shows further preferences, including custom commands, proxy and download manager settings, and filename handling, so it is worth a quick pass through the page after installation.
Is The Stream Detector still maintained?
The Stream Detector is no longer in active development. The developer archived the GitHub repository in July 2023 with version 2.11.7, stating that development is on hold, although serious issues might still be addressed. The add-on remains available on Mozilla Add-ons, where it has roughly 15,000 users and a 4.3 rating.
A Chrome port with the same name and version number is listed in the Chrome Web Store. Its listing says it is a Firefox add-on ported to Chrome and that it lacks certain features of the Firefox version, and the GitHub README describes the Chrome port as not maintained or supported. Firefox is the version to use if you have the choice.
An unmaintained add-on still works as long as browser APIs and sites do not change, but expect detection on some sites to break over time with no fix coming.
Permissions and privacy
The Stream Detector asks for broad permissions because it has to see network requests on every site you visit. Mozilla Add-ons lists the following:
- Access your data for all websites (needed to see stream requests)
- Access browser tabs (to sort streams by tab and use tab titles)
- Download files and read and modify the download history (for direct downloads)
- Write data to the clipboard (to copy URLs and commands)
- Display notifications
These permissions match what the add-on does, and the source code is public for anyone who wants to check it. Because the copied commands can include your session cookies, treat them like a login token: do not paste them into public forums or bug reports.
Limits and lawful use
The Stream Detector works on sites that serve standard, unencrypted HLS or DASH streams, and it does not work around copy protection. The developer notes that major platforms such as YouTube, Vimeo and Facebook very likely use proprietary technologies the add-on does not support, and that copyrighted content is usually DRM protected anyway. Streams protected with DRM cannot be saved with it, and you should not try to circumvent that protection.
Legitimate uses include:
- Testing and debugging your own HLS or DASH streams and players
- Opening a public live stream in VLC or another player you prefer
- Recording your own webinars, lectures or broadcasts
- Archiving openly licensed or public domain media where the site's terms permit it
- Grabbing subtitle files for accessibility from content you are allowed to use
Before you save anything, check the site's terms of service and the copyright status of the content. Being able to copy a stream URL does not mean you have the right to download the stream.
FAQ
Why does The Stream Detector show no streams?
Start playback first, since many players request the playlist only when the video starts. If the list stays empty, the site probably uses a proprietary or encrypted delivery method the add-on cannot detect.
Is The Stream Detector free?
Yes. The add-on is free, contains no paid tier and is open source under the Mozilla Public License 2.0.
Do I need yt-dlp or FFmpeg to use it?
No. You can copy the plain stream URL and open it in a player that supports HLS or DASH. The command formats are only useful if you have the matching tool installed.
Related: the best Firefox add-ons, Neat Download Manager with media grabbing, converting video files with Shutter Encoder
Nice find, Martin!
There is a version for Chromium (CRX file) on the Github page of the project: https://github.com/rowrawer/stream-detector/releases
Very interesting addon, thanks! :]