Free Subtitle Generator that runs in your browser
Drop a video or audio file. Whisper AI transcribes it on your own device — no upload, no sign-up, no waiting for a server. Download SRT/VTT, then turn the same transcript into chapters, Shorts ideas, carousels and social posts in one click.
🎬 1 · Generate Subtitles
Your captions (click any line to edit)
♻️ 2 · Repurpose Studio
One video → a week of content. Uses the transcript above — or paste any script/text of your own:
How it works
- You pick a file. It stays on your device — Captio never uploads it anywhere.
- Whisper AI runs in your browser (via Transformers.js + WebAssembly/WebGPU) and writes timestamped captions.
- You edit & download SRT/VTT for YouTube, Premiere, CapCut — or repurpose the words into more content.
FAQ
Is it really free and private?
Yes. The AI model runs 100% on your device. There is no server receiving your audio or video — you can even disconnect the internet after the model loads and it still works.
How accurate is it?
Captio's free tier uses the Whisper "tiny" model — fast and good for clear speech. You can fix any line in the built-in editor. A higher-accuracy model is planned for the premium tier.
Which formats can I use the subtitles in?
SRT works with YouTube, Facebook, Premiere Pro and most editors. VTT works on the web and in many players. You can also preview captions directly on your video above.
How long can my file be?
Processing happens on your device, so it depends on its power. Shorts and clips up to ~10 minutes are quick; longer files work too but take longer. A 200 MB file-size safety limit applies.