Free tool
Add subtitles to WebM
To add subtitles to WebM videos, bring the WebM and its SRT or VTT. The captions are burned into the picture, which is re-encoded as VP9 so the file stays a WebM, with the sound copied. For a video on a web page, a separate VTT file can do the job without re-encoding.
- Free
- Stays a WebM
- Nothing is uploaded
1. The video
Drop your WebM video here, or Choose your WebM video
MP4, MOV, WebM or MKV, up to 2 GB and 3 hours. Everything happens in your browser; nothing is uploaded.
2. The subtitles
SRT, VTT, SBV or ASS. No subtitles yet? Make them from the video with the subtitle generator.
How it works
How do you burn subtitles into a WebM?
Choose the WebM and the subtitle file, set the caption size, look and position, and check one in the preview. Press Burn in subtitles: each frame is decoded, the caption drawn on it and the frame encoded again as VP9, while the Opus sound is copied.
- 1
Choose the WebM and the subtitles
SRT, VTT, SBV or ASS; drop both together if you like.
- 2
Keep WebM, or pick another format
Save as WebM, or as MP4 or MOV if the video is going somewhere WebM isn’t played.
- 3
Burn in and download
A bar shows the progress; the WebM plays in the page when it’s done.
Is burning in the best way to caption a video on your website?
Usually not. A web page can show captions from a separate VTT file over the video with a track element, which every browser supports: viewers can turn them off or pick a language, and the video isn’t re-encoded. Burn them in when the WebM will be shared outside your page.
- 1
Convert the subtitles to VTT
An SRT becomes a VTT with the [SRT to VTT converter](/tools/srt-to-vtt); the captions and times stay the same.
- 2
Add a track element
Inside the video element, point a track at the VTT file with its language.
- 3
Keep the WebM as it is
No re-encoding, so the video keeps its quality and its size.
Why not put a subtitle track inside the WebM?
Because browsers, where WebM is mostly played, don’t show it: neither Chrome nor Safari listed a subtitle track stored inside a WebM when we tried. So this tool doesn’t write one. For a desktop player, choose Subtitle track and save as MKV, with the captions as an SRT track.
How long does burning subtitles into a WebM take?
Longer than for an MP4, because VP9 is slower to encode than H.264. Our 30-second 720p WebM took 2.9 seconds in Chrome’s engine and 6 to 10 in Safari’s, on a Mac with Apple silicon; the time grows with the video’s length and picture size.
Where do captions for recorded talks come from?
From a transcript. NoteOwl transcribes a recording on your Mac with each speaker labelled and exports SRT; burn it in here, or make it a VTT for your page’s video. The subtitle generator makes one in the browser too.
FAQ
Questions about adding subtitles to a WebM
Is my WebM uploaded?
No. The WebM and the subtitles are read from your device and the new video is encoded in the page. In our tests no network request left the browser while it worked.
Does burning in lower the quality?
Slightly, as any re-encode does. The VP9 bitrate is set for the video’s size and frame rate so the picture looks the same; the Opus sound is copied as it is, without any change.
Can I get an MP4 with the subtitles instead?
Yes. Choose MP4 under Save as: the picture is re-encoded as H.264 with the captions in it and the Opus sound becomes AAC, so it opens in QuickTime Player, iMovie and on phones.
Does it work with a VP8 WebM?
Yes. VP8 and VP9 WebMs both decode in Chrome, Edge and Safari; the subtitled video is written as VP9 either way.
Will a VTT track work with a WebM on my page?
Yes. A track element works the same with WebM and MP4 sources, so one VTT file captions both. Convert an SRT with the SRT to VTT converter first; the times stay the same.
What if the captions are out of sync with my WebM?
Shift them first: the subtitle shifter moves every caption earlier or later, or re-syncs a file that drifts. Then burn them in, or use the VTT on your page.
Keep exploring
Add subtitles to video
- Add subtitles to videoBurn an SRT, VTT or ASS file into a video, or add it as a subtitle track, in your browser; long lines, two-line captions, any script, right to left
- Add subtitles to MP4Add an SRT or VTT to an MP4 in your browser: burned into the picture for social posts, or as a subtitle track QuickTime and Safari can switch on
- Add subtitles to MOVBurn subtitles into an iPhone or QuickTime MOV in your browser, upright on portrait videos, and keep it a MOV
Related
- SRT to VTT converterConvert SRT to VTT, VTT to SRT, or either to clean text with each speaker’s lines merged, in your browser; Zoom and Teams transcripts work
- MP4 to WebM converterConvert an MP4 to a VP9 and Opus WebM in your browser, for a web page’s video or anywhere WebM is asked for
- Subtitle generatorA free AI subtitle generator: drop in a video or recording and download SRT or VTT subtitles timed to the speech, two short lines per cue; only the sound is sent, nothing is stored
Captions from your recordings, made on your Mac
Free to download. Runs entirely on your Mac.
macOS 26 or later · Apple Silicon (M1 or newer) · 16 GB memory minimum, 24 GB recommended
About NoteOwl
NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.
NoteOwl pricing: what’s free and what Pro adds
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