Video Format Converter changes one container and codec into another: MOV files from Apple devices, WebM from screen recordings, downloaded MKV or old AVI become an MP4 that plays anywhere, or the other way round into web-friendly WebM. It is the “Video conversion” tab of the audio/video workbench, and ffmpeg inside the browser does all the work.

Each target format maps to a fixed codec pair: MP4 / MKV / MOV / FLV / TS use H.264 + AAC 128 kbps; WebM uses VP9 + Opus (noticeably slower to encode); AVI uses MPEG-4 (Xvid) + MP3; 3GP uses H.264 baseline + AAC 96 kbps; OGV uses Theora + Vorbis. Every conversion re-encodes the picture — there is no copy mode that only swaps the container.

1. 01Add and select a video— drop it into the workbench, click it in the left-hand list and switch to “Video conversion”; the three cards at the top are one-click presets and the fields below are custom parameters, and the two do not affect each other.
2. 02Pick the target format— click MP4, WebM, MKV, AVI, MOV, FLV, TS, 3GP or OGV; the codec pair for each one is written under the card.
3. 03Adjust quality and specs— drag “Quality CRF” (18–32, default 23), choose an encoding speed preset (ultrafast to slow, default fast), a resolution (original / 1080p / 720p / 480p, shrink only) and a frame rate (original / 30 / 24).
4. 04Start converting— click “Start conversion”; with several videos loaded a “Convert all N videos” button also appears. When the output extension matches the source, the file name gets a _converted suffix.

Always re-encoded

— even a container-only change such as MP4 to MKV re-compresses the picture, at a small cost in quality and with a runtime that scales with the video's length

Decoding limits

— AV1 sources cannot be decoded (an error appears when you start); WMV, RMVB, MPG and MTS can be used as input but only convert to the nine targets above

Resolution and frame rate

— resolution is only ever reduced, never enlarged; frame rate has just two fixed values, 30 and 24, with no 60 fps

Subtitles and extra audio tracks

— only the default video stream and audio stream are handled, so subtitle tracks and a second audio track inside an MKV are left out of the output

What it does not do

— it is not a compression tool (use Video Compression to shrink by size), it does not extract audio (use Extract Audio) and it does not make GIFs (use Video to GIF)

The conversion runs in your browser through ffmpeg.wasm and the video never leaves your machine; the first use downloads about 31 MB of engine files from a CDN (the site's asset domain or jsDelivr), which are then reused within the same page, and that download carries no file content.