How to compress MP4 files online
- Select or drop your .mp4 file.
- Keep Medium quality, or switch to Target file size for an exact MB limit.
- Choose 1080p or 720p if the source is 4K.
- Compress and download the smaller MP4.
Why MP4 files get so big
MP4 is just a container; the size depends on the video codec and bitrate inside it. Cameras and phones record at high bitrates so footage survives editing. For sharing, that headroom is wasted space. Re-encoding at a sensible bitrate for the resolution — which is what ShrinkVid does — removes it.
HEVC (H.265) MP4s from iPhone
iPhones save HEVC video. HEVC is already efficient, so the size drop comes mainly from the lower bitrate and optional resize. ShrinkVid outputs H.264, which is less efficient than HEVC at the same bitrate but plays on every device, browser, Windows PC and social network without extra codecs.
Recommended settings for common uses
| Goal | Settings |
|---|---|
| Share in chat apps | Medium · 720p |
| Upload to a website | Medium · 1080p · MP4 |
| Email attachment | Target size 20–24 MB · Auto resolution |
| Archive with little loss | High · Original resolution |
Private by design
ShrinkVid never uploads your files. The page loads once, then all decoding and encoding happens on your device using the browser’s built-in WebCodecs API (hardware-accelerated video) and WebAssembly image codecs. That makes it safe for personal, confidential or work files — and there is no queue, no file size cap and no watermark. Read how it works.
Frequently asked questions
Are my files uploaded to a server?
No. ShrinkVid runs entirely in your browser. Files are read and encoded on your own device with WebCodecs and WebAssembly, so nothing is uploaded, stored or seen by anyone else. You can even disconnect from the internet after the page loads and it keeps working.
Can I compress an MP4 without losing quality?
Truly lossless compression barely reduces video size. The High preset is the closest practical option — it keeps the original resolution and a generous bitrate, so differences are very hard to see while the file is still noticeably smaller.
Why is my compressed MP4 not much smaller?
The source was probably already compressed efficiently (for example a download from a streaming site). Lower the resolution to 720p or switch to Low quality for a bigger reduction.
Is it really free? Is there a watermark or file size limit?
It is completely free with no watermark, no sign-up and no server-side file size limit. Because processing happens on your device, the only practical limits are your device’s memory and speed.
Last updated · by the ShrinkVid team