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This is a free online video compressor that shrinks MP4, MOV, MKV, WebM, AVI, FLV and MPEG-TS files entirely in your browser. It is built for the situations cloud tools handle badly: sending a large recording over email or chat, fitting footage under an upload cap, prepping screen recordings and gameplay for the web, and compressing footage you simply cannot put on someone else's server. Unlike Clideo it adds no watermark, unlike Kapwing and Veed it imposes no file-size or duration cap, and unlike FreeConvert it never uploads the file in the first place — so compression starts immediately, regardless of file size.

How it works

There is no server-side ffmpeg and no ffmpeg.wasm download. A small WebAssembly build of ffmpeg's libavformat demuxer (web-demuxer) runs in a worker inside your tab and splits the container into encoded video and audio packets. Your browser's native WebCodecs decoders then unpack the frames, and its hardware-accelerated VideoEncoder re-encodes them at the new bitrate, resolution and frame rate, while AudioDecoder/AudioEncoder handle the sound track (with linear resampling and downmixing when needed). A tiny JavaScript muxer — mp4-muxer or webm-muxer — writes the finished container, with fast-start (moov atom first) so playback begins instantly. The engine and muxer libraries are fetched once from a pinned CDN URL on first use and cached by the browser; your video is never part of any request.

Outputs, codecs and settings

Four output combinations are offered depending on what your browser can encode: H.264 in MP4 for universal playback (the safe choice for sharing), AV1 in MP4 or WebM for the smallest files, and VP9 in WebM for web-native video. At the same visual quality AV1 typically needs around 45% fewer bits than H.264, with VP9 in between; newer codecs are also slower to encode. Quality mode maps the 1–100 slider to a bits-per-pixel-per-frame budget scaled by each codec's efficiency, while target-size mode works backwards from your megabyte goal and the clip's duration to derive a video bitrate, reserving room for audio and container overhead. Resolution caps (2160p down to 480p, applied to the long edge so portrait video is handled correctly), frame-rate caps (30/24 fps), and an optional audio drop provide the big structural levers. The estimated output size updates live before you start, and warns when a source is already so efficient that the chosen settings may not shrink it.

Audio is re-encoded to AAC at 96 kbps stereo (64 kbps mono) in MP4, or Opus in WebM. Display rotation from phones is preserved in MP4 output, and dimensions are always rounded to the even numbers codecs require.

Limits & requirements

The tool needs the WebCodecs API: current desktop Chrome, Edge, Arc and Opera support every offered codec, and Safari supports it from version 16.4 (with a smaller codec set). Decoding the source also depends on the platform: H.264, VP9 and AV1 are broadly supported, while HEVC/H.265 only decodes where the operating system licenses it — recent macOS/iOS Safari and HEVC-capable Chrome builds. Whatever the input, output is always re-encoded to H.264, VP9 or AV1 for compatibility. Re-encoding is lossy by nature, so keep an original if you may need another export later, and expect AV1 encodes to run noticeably slower than H.264 on the same machine. Encode speed (shown live as a multiple of real-time) and memory use scale with source resolution and duration, but there is no artificial file-size ceiling.

Privacy

The video is read from your local disk by code running inside the browser tab and never leaves the device. There is no upload progress because there is no upload: the only network requests are one-time static downloads of the demuxer engine and muxer libraries. Nothing is logged, stored, analysed, or watermarked, and no account exists.