Why compress instead of re-recording
Most video compression problems are actually upload-limit problems. A phone records at 20-60 Mbps, which means a one-minute 1080p clip is routinely 100-200 MB. Then it has to go somewhere that accepts 10 MB, or 16, or 25. Re-recording at lower quality wastes the original; running the file through a conversion service means handing your footage to someone else's server.
This tool takes the third option. Your browser reads the file, encodes it with FFmpeg compiled to WebAssembly, and hands back a download. The file is never transmitted, so there is no upload wait and nothing to trust a third party with.
Two ways to choose a size
Platform presets target a known limit. Discord's free tier caps attachments at 10 MB, WhatsApp media messages at 16 MB, most mail servers at 25 MB. Pick one and the tool works out the bitrate needed to land under it, capping resolution where that produces a better result than crushing quality at full size.
Exact target size is for when you have a specific number. Enter the megabytes and the bitrate is derived from the clip's duration, with roughly 8% held back for container overhead so the output lands under the ceiling rather than just over it.
What this tool will not do
It will not make an hour of 4K footage fit into 10 MB at watchable quality — no encoder can. When a target is physically impossible, the result is blocky and the tool will not pretend otherwise. For long or high-motion video, either accept a larger output, split the clip, or lower the resolution explicitly.
It is also not a video editor. There is no trimming, cropping, subtitle burn-in or audio replacement. It compresses what you give it.
Limits worth knowing
Processing happens on your CPU, so speed scales with your hardware and memory is the real constraint — not a server quota. Files under 500 MB are comfortable on a laptop; phones may fail well before that. First use downloads a 32 MB engine, which the browser then caches.
Frequently asked
Are my videos uploaded anywhere?
No. The site is static — there is no backend that accepts video. Your browser reads the file from disk, processes it locally, and produces a download backed by memory. Close the tab and nothing remains.
Why did my video barely shrink?
If the source is already efficiently encoded — a phone export at a sensible bitrate, or something that has been compressed before — there is little left to remove at the same resolution. Reducing resolution is where the real savings come from: try the Strong preset, or set a target size and let the tool lower the bitrate deliberately.
Does it cost anything?
No. No account, no quota, no watermark. The site is supported by a single ad.
Which formats are supported?
MP4, MOV, MKV, WebM, AVI, M4V, WMV and MPEG go in. Output is always MP4 with H.264 video and AAC audio, because that combination plays everywhere.
Can I compress several files at once?
Yes — drop a batch and they are processed one after another. They run in sequence rather than in parallel, because the WebAssembly encoder is single-threaded and running several at once only exhausts memory faster.