Free AI subtitle generator · 100% in your browser

Generate subtitles and burn them in

This AI subtitle generator automatically transcribes your video, then burns the subtitles onto the picture, entirely on your device.

How to add subtitles to a video (free AI subtitle generator)

1
Import your video
Drop your file. It stays on your device, nothing is uploaded.
2
Generate & burn
Click “Generate & burn subtitles”. Montaj transcribes the audio with AI, then burns the timed lines onto the picture.
3
Get your MP4
Save the video with subtitles burned in, ready to post. Captions included wherever it's shared.

Frequently asked questions

How do I add subtitles to a video for free?

Import your video and click “Generate & burn subtitles”. The audio is transcribed by an on-device AI model and the lines are burned onto the picture automatically, no account, no watermark, no fee.

Is my video uploaded to a server?

No. Both the transcription (Whisper) and the subtitle burn-in run entirely in your browser, on your device with ffmpeg.wasm. Nothing is sent anywhere.

Which languages are supported?

Auto-detect, English, French, Spanish, German, Italian and Portuguese.

Can I choose where the subtitles appear?

Yes. Pick top, center or bottom before you generate.

How accurate is the transcription?

It uses an on-device Whisper model. Accuracy is very good for clear speech but can vary with heavy accents, background music or overlapping talkers.

Is this an automatic subtitle generator?

Yes, as a video subtitle generator it needs zero manual typing. Transcription and subtitle placement both happen automatically; you only pick the position and language.