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Auto caption generator

Generate captions for a video automatically and burn them in, with no watermark. Free, with no upload.

Files stay on your device

Drop a video to caption it automatically

The captions are written from the speech on your device, so nothing is uploaded.

Any media file this browser’s engine can read.

How to auto caption a video

Open a video and its captions are written from the speech on your device. Fix any word, pick a style, and save the captioned video for Reels, TikTok, or YouTube Shorts, or download the captions as an SRT file.

  1. Step 1

    Choose a video
    Captions are written from its speech on your device.

  2. Step 2

    Check and style them
    Fix any word, then pick a size and a look.

  3. Step 3

    Download the video
    Save it with the captions burned in.

What to expect

Supported inputs
Videos with sound that this browser can read.
What happens
Captions are drawn into every frame and the video is re-encoded in its source format; the sound is copied as it is.
Limits
The first time, the browser downloads the 77 MB speech model and keeps it. Captioning takes about a sixth of the video's length.

Private by design

Your video stays on your device

Mastershot processes your file locally in this browser. It does not need to be uploaded to a server, and you do not need an account to use the tool.

  • No upload
  • No signup
  • No watermark

Questions

No. The captioned video is yours, with nothing added.

Yes. Captions are burned into the picture, so they show wherever the video is posted.

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