Video Compressor Online
Shrink a video by scaling its resolution and adjusting quality, and see exactly how much you saved — all without uploading the file anywhere.
How does this video compressor work?
A full build of FFmpeg, compiled to WebAssembly, runs inside your browser tab. Your file is re-encoded with the H.264 codec at the resolution and quality level you pick, and written back out as an MP4. Two controls do the heavy lifting: scaling the resolution cuts the number of pixels that need encoding, and the quality setting adjusts the constant rate factor, which tells the encoder how aggressively it may discard detail to save space.
GuideHow to use it
Features & benefits
Why this runs entirely in your browser
Video compression services normally require you to upload a large file and trust a stranger's server with it. Here, the encoder comes to your video instead: the FFmpeg engine downloads once into your browser, and your footage never moves. Compression is slower than a datacentre would be — your CPU is doing the work — but nothing is transmitted, there is no queue, and no server holds a copy of your file afterwards.
Common uses
Getting a video under an email or messaging attachment limit, shrinking a screen recording before uploading it to a ticket or a chat, reducing a phone clip that is needlessly large for the way it will be viewed, preparing lighter video for a website, or freeing up storage space on footage you want to keep but not at full resolution.
Frequently asked questions
A few things people usually want to know before compressing a video.
It sets the constant rate factor, or CRF, which is how H.264 decides its own bitrate. Lower CRF means higher quality and larger files; higher CRF means more compression and visible softening. High quality here uses CRF 20, which is close to visually lossless for most footage; Balanced uses CRF 26, a good default that typically produces a fraction of the original size; Small file uses CRF 32, which is noticeably compressed but fine for previews and quick shares. CRF adapts the bitrate scene by scene, so simple footage shrinks far more than busy footage.
Reducing resolution is usually the bigger win, because halving the height and width removes three quarters of the pixels to be encoded. If your video will be watched in a small player, on a phone, or embedded in a document, dropping a 4K or 1080p source to 720p typically saves far more than any quality tweak while looking essentially the same at that display size. Keep the original resolution and lean on the quality setting only when the footage will be viewed full-screen on a large display.
Unlike trimming, compression must decode every frame and re-encode it, and that work runs on a single browser thread on your own CPU rather than in a datacentre. A short clip finishes in under a minute, while a long or high-resolution video can take several minutes or more. The progress bar reflects the encoder's real position in the file. Choosing a lower target resolution speeds things up considerably, since the encoder has far fewer pixels to process per frame.
The output is always an MP4 with H.264 video, the most broadly compatible combination available — it plays on virtually every device, browser, and editor. Yes, output can occasionally exceed the input: if your source was already heavily compressed and you select High quality at the original resolution, the encoder may spend more bits than the source did. The size comparison shown after each run makes this obvious, so if it happens, re-run with a smaller resolution or a more aggressive quality setting.
No. Your video is never uploaded, stored, or shared. It is read from your device into browser memory, re-encoded by FFmpeg running as WebAssembly inside this tab, and written back out locally as a downloadable file. The only network request the tool makes is fetching the FFmpeg engine itself, which contains none of your data and is deferred until you actually press Compress. Closing or refreshing the page discards the source and the compressed result immediately.