Video Converter

One converter for the formats people still run into: phone videos in MOV, downloads in MKV or WebM, camcorder AVI and MPEG files, WMV from old Windows PCs, FLV and 3GP from the early web. Pick the output format and the converter chooses matching codecs. When the video and sound already suit the new container they are copied as they are — fast and lossless — and otherwise re-encoded. Everything runs in your browser with ffmpeg (about 30 MB, downloaded once); files are not uploaded.

How to use this tool

1. Choose one or more videos.
2. Pick the output format. MP4 is the safest choice for phones, TVs, editors and uploads.
3. Optionally lower the resolution or choose a quality level (only used when re-encoding).
4. Press Calculate, follow the progress bar, then download the result or a ZIP of all results.

Formula

Copy when (source codec ∈ codecs the container accepts) and size is kept; otherwise re-encode

MP4, MOV and FLV use H.264 with AAC; WebM uses VP8 with Vorbis (the in-browser engine has no working VP9 or Opus encoder); AVI uses Xvid (MPEG-4 Part 2) with MP3; WMV uses Windows Media Video 8 with WMA; MPEG uses MPEG-2 with MP2 at a standard frame rate; OGV uses Theora with Vorbis; 3GP uses baseline H.264 at up to 480p. MKV accepts almost anything, so it is nearly always a copy.

Example

An MKV film with H.264 video and AAC sound converted to MP4 is a straight copy: a 1.4 GB file comes out at about 1.4 GB in well under a minute. The same film converted to WebM must be re-encoded frame by frame, which in a browser runs at only a few frames per second at 1080p.

Speed and limits

Copying is limited only by memory: a 1.2 GB file is repackaged in well under a minute on a computer. Re-encoding runs on one processor core: on a recent computer expect about 12 frames per second at 720p with H.264, about 15 with WebM (VP8) and about 7 with Theora. Portrait phone videos are always re-encoded for MKV, WebM, AVI and FLV, because only MP4 and MOV can store their rotation flag. AV1 video cannot be decoded by this engine, so it can only be copied (into MKV, WebM or MP4).