Compress video in your browser
Re-encode an MP4, MOV, WebM or MKV file at a lower resolution, frame rate or quality to make it dramatically smaller. The encoding uses your own CPU and GPU — no upload, no queue, no daily quota.
How to compress a video
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Add the file The browser opens it from your disk. A long video is fine — the file is streamed, not loaded into memory all at once.
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Drop the resolution and the quality Going from 1080p to 720p roughly halves the pixel count. Moving from High to Medium quality typically cuts another 30–40%.
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Convert and download The result card shows the new size and the percentage saved against the original.
What actually makes a video smaller
File size is bitrate multiplied by duration. Nothing else matters as much. Bitrate is driven by three things you control here:
| Lever | Typical saving | Cost |
|---|---|---|
| Resolution 1080p → 720p | 40–55% | Softer on large screens |
| Resolution 1080p → 480p | 70–80% | Visibly soft; fine for messaging |
| Quality High → Medium | 30–40% | Some fine detail is lost |
| Frame rate 60 → 30 fps | 30–45% | Motion looks less fluid |
| Trimming the length | Proportional | You lose the removed part |
Stacking them multiplies: 1080p60 at high quality moved to 720p30 at medium quality usually lands at around 20–25% of the original size, and is indistinguishable on a phone.
Choosing a container
MP4 (H.264) is the safe default — it plays in every browser, on every phone, in every editor and on every TV. WebM (VP9) is usually 20–30% smaller at the same visual quality but is awkward outside the web. MKV is a container, not a codec: it can hold whatever the source used, which makes it a good choice when you want to re-wrap without re-encoding quality loss.
One caveat about hardware: browsers expose whatever encoders the operating system provides. H.264 encoding is hardware-accelerated almost everywhere. VP9 and AV1 encoding is less consistently available — if the conversion fails immediately, switch the output to MP4.
Frequently asked questions
How much smaller will my video get?
It depends on the source. A phone video recorded at a high bitrate can shrink by 80% with no visible difference at phone size. A video that was already compressed hard may only drop 20–30%. The result card shows the exact percentage each time.
Does compressing twice ruin the quality?
Every re-encode is a generation loss with a lossy codec. Compress once, from the best source you have, and keep the original. If you need to iterate, work from the original each time rather than from an already-compressed copy.
Why does the tab use so much CPU?
You are the encoder. A server farm would spread the work across dedicated machines; here your laptop does it, often with hardware acceleration but still at full tilt. Expect the fan to spin on long files.
Is there a length limit?
No hard limit from the tool. The practical one is memory: the finished file is assembled in RAM before download. Very long videos on a machine with 8 GB of RAM may fail — split them or trim first.
Can it compress a video that is already HEVC or AV1?
Decoding depends on your browser and hardware. Safari decodes HEVC well; Chrome on Windows often does too if the codec pack is installed. If the file cannot be decoded, the error message will say so — convert it to H.264 elsewhere first.
Is anything uploaded?
No. The whole pipeline — demux, decode, scale, encode, mux — runs in the tab. You can confirm with the Network panel in DevTools.