Add Subtitles to Video (Caption Burner)

About Add Subtitles to Video (Caption Burner)

The Caption Burner adds subtitles to a video and burns them into the picture permanently (open captions) — entirely in your browser. Load an existing SRT or VTT file, or let an on-device Whisper AI model auto-transcribe the audio, then edit the text, pick one of three caption styles (clean bar, bold Shorts-style outline, or minimal shadow), set the size and position, and export an MP4 with the captions hardcoded into every frame. The video is decoded, drawn and re-encoded with WebCodecs on your device, so nothing is uploaded and there is no watermark or length limit beyond your browser's memory.

How to use Add Subtitles to Video (Caption Burner)

1. Drop in a video (MP4, WebM, MOV or MKV) — it is read locally and its dimensions and duration appear.
2. Add captions: upload an SRT or VTT file, or switch to Auto-generate to transcribe the audio with on-device Whisper (desktop browsers; pick the spoken language for best accuracy).
3. Fix any wording right in the cue list — every caption is editable and deletable, and you can download the corrected SRT for reuse.
4. Pick a style — Clean bar, Bold outline (the Shorts/TikTok look) or Minimal shadow — then set the text size and the bottom/center/top position. The live preview shows exactly what will be burned in.
5. Click Burn captions into MP4 and watch the progress bar; every frame is re-encoded with the captions drawn in while the audio track is copied untouched.
6. Save the captioned MP4 — it plays with subtitles visible everywhere, on every player and every platform.

Frequently asked questions

Is my video uploaded to a server?

No. The video is decoded, captioned and re-encoded entirely on your device with WebCodecs. Even the auto-caption AI runs locally: an open Whisper model downloads once from a public CDN and then transcribes in your browser — your video and audio never leave the page.

What's the difference between burned-in and soft subtitles?

Burned-in (open) captions are drawn into the video frames themselves, so they show up on every player and platform and can never be turned off — ideal for social feeds that autoplay muted. Soft subtitles live in a separate track or SRT file that players can toggle, but many platforms and embeds ignore them. This tool burns them in; it also lets you download the edited SRT if you want the soft version too.

Do auto-captions work on phones?

Auto-transcription needs a desktop browser — the on-device Whisper model is too heavy for phone tabs. Uploading an SRT/VTT file and burning it in works everywhere, including on your phone.

Which style should I use for Shorts, Reels and TikTok?

Use the Bold outline preset — heavy white text with a thick black outline stays readable over any footage, which is the standard look for Shorts, Reels and TikTok. Bump the text size to around 5–6% of the video height and keep the position at bottom or center.

Can I fix caption timing here?

You can edit and delete caption text right in the cue list. For timing work — shifting everything by a second, two-point drift sync, or reading-speed QC — open the Subtitle Converter & Editor, fix the timing there, download the SRT and load it back into this tool.