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MP4 to SRT

Get SRT subtitles from an MP4: embedded tracks are reused, otherwise Whisper AI transcribes the speech in your browser.

How it works

  1. 1

    Drop your file into the box above. It is opened locally, never uploaded.

  2. 2

    The first run downloads the AI model once; your browser caches it for next time.

  3. 3

    Review the result in the editor, then download it in the format you need.

Frequently asked questions

Is MP4 to SRT free?

Yes. Every tool on FastSub AI is free, with no sign-up, no watermark and no usage limits.

Are my files uploaded anywhere?

No. Your files are read and processed inside your browser tab. The only downloads are the app itself and, for AI tools, the model files.

Why does the first run download a model?

The AI runs on your own device, so the model has to be on it. It downloads once and your browser keeps it cached, so later runs start straight away and even work offline.

Which browsers work best?

Any modern browser works. AI tools are fastest in Chrome or Edge on a desktop with WebGPU; other browsers fall back to the CPU, which is slower but works.

Is there a file size limit?

Subtitle files up to 20 MB and videos up to several GB, limited only by your device's memory.

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