Add Subtitles to Video

Put subtitles on a video so they show everywhere — on Instagram, TikTok, in a presentation or a chat — or add them as a track that viewers can switch on and off. Choose an SRT, WebVTT or ASS file (or paste the text), then the video. Burned-in subtitles are drawn with your computer's own fonts, so Korean, Japanese, Chinese and accented text all work, with the size, colours, style and position you choose. Everything happens in your browser with the ffmpeg engine (about 30 MB, downloaded the first time); nothing is uploaded.

How to use this tool

1. Choose the subtitle file, or paste SRT/VTT text into the box.
2. Pick "Burn into the picture" (always visible) or a switchable subtitle track, and for burn-in the size, style, colours and margin.
3. Choose the video last; the result is made right away.
4. Play the result in the page and download it.

Formula

Burn-in: each subtitle → transparent picture shown from its start to its end time → overlaid on every frame → H.264 MP4

Overlapping subtitles are shown together, stacked. Cues marked for the top of the screen ({\an8} in SRT, line:0 in VTT, top alignment in ASS) are drawn at the top. A track is added without re-encoding: MP4 stores it as a mov_text track (which cannot overlap, so overlapping subtitles become one joint subtitle), MKV as SRT, or as the original ASS with its styling. Burn-in re-encodes the picture (CRF 20 by default) and copies AAC or MP3 sound.

Example

A 3-minute 1080p interview with 48 subtitles burned in at the medium size gets text about 59 px tall (5.5% of 1080). Encoding at about 6 frames per second takes roughly 15 minutes for 5,400 frames; adding the same subtitles as an MP4 track takes a couple of seconds.