Compress MP4 files
Pick the exact size you need and drop your MP4 — compression runs on your own device at hardware speed.
Drop your video here
or
MP4, MOV, WebM, MKV, AVI and more — any size, no upload
🔒 Files never leave your device — everything runs in your browser.
MP4 is the format everything speaks, but not every MP4 is efficient: a file's size depends on the bitrate it was encoded with, and cameras, phones, and editing exports routinely use two to five times more bits than the picture actually needs. That headroom is why an MP4 can often shrink dramatically with little visible change.
ConvertUno re-encodes your MP4 with a hardware-accelerated H.264 encoder tuned to a byte target rather than a vague quality slider — you say what the file must weigh, and the output is guaranteed to land under it. When the budget is generous the resolution is preserved; when it is tight, the tool steps down the ladder honestly and tells you what it did.
How it works
- Drop your file
Any common format, any size. Nothing is uploaded — the tool runs in your browser.
- Pick your target
Use the presets above — this page's defaults are tuned for compress mp4 — or type any size.
- Download
Your converted file is ready on your device — nothing to wait for, nothing to delete from a server.
Frequently asked questions
Will compressing an MP4 lose quality?
Re-encoding always costs something, but from a typical generously-encoded source the difference at half or even a quarter of the size is hard to spot at normal viewing. Quality falls off only when the target forces a very low bitrate — and the tool protects watchability by reducing resolution before it lets the image smear.
Does it stay an MP4 after compression?
Yes — output is a standard MP4 with H.264 video and AAC audio, the most universally playable combination that exists: every browser, phone, TV, and chat app opens it.
Is there a file size limit for the input?
No. Because your file is processed on your own device rather than uploaded, multi-gigabyte MP4s work fine — processing time simply scales with the video's duration.
Is my file uploaded to a server?
No. ConvertUno runs entirely in your browser on your own device. Your file never leaves your computer or phone — there is no upload at all.
Is it really free, with no watermark?
Yes. Processing happens on your device, so serving you costs us almost nothing — no watermark, no account, no file-size limit, no daily quota.