OpenSubs by OpenSubs

Free, open-source live subtitles for videos playing in your tab. Local Whisper AI — no account, no upload, no API key required.

Experimental

Available on Firefox for Android™

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About this extension

OpenSubs is a free, open-source subtitle tool: it transcribes whatever plays in your tab as it plays, using a local Whisper model. Audio never leaves your device.

Simple to use: start the video, click the OpenSubs icon, hit Start. Subtitles appear over the page as each part is transcribed, and the overlay shows how far behind the speech they are.

Features
• No website access at install — granted for the current site only, and only when you hit Start
• Runs on WebGPU or CPU — Tiny, Base, or Small models
• No account, no sign-up, no API key
• Works on pages that play video or audio in the page itself: video sites, lecture recordings, recorded talks
• Automatic language detection, or pick it yourself
• Subtitle overlay you can turn off
• Export as SRT
• AGPL-3.0 open source

OpenSubs is built for people who would rather not send audio to the cloud: students rewatching lecture recordings, viewers working through content in another language, anyone in a noisy room, and anyone who cares about privacy.

Beyond the extension, OpenSubs is also available as a desktop app for macOS, Windows and Linux, and as a web app at opensubs.app. Everything that runs on your own machine is free.

GitHub: https://github.com/open-subs/opensubs

Developer comments

How to use
1. Play a video in any tab.
2. Click the OpenSubs button and press Start. Firefox asks for access to that site once.
3. Subtitles appear at the bottom of the page. Press Stop, then Save .srt to keep them.

The first run downloads the speech model once (Tiny ~40 MB, Base ~80 MB, Small ~250 MB). After that it runs fully offline on your computer.

Known limitations
- Videos inside a player embedded from another site (cross-origin iframe) can't be read. Open the video on its own site instead.
- DRM-protected streams can't be captured.
- On slower machines, pick the Tiny model or Processor (CPU) if subtitles fall behind.

Privacy
Audio never leaves your computer. No account, no tracking.

Open source (AGPL-3.0) · Bug reports: [GitHub URL]

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OpenSubs by OpenSubs

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