Compress MP4 lowers the bitrate of an MP4 video so the file gets smaller while it keeps playing everywhere. Choose 30%, 50% or 70% smaller, or a target size, and the video is re-encoded by your browser’s own encoder, without uploading it anywhere.
Why MP4 files get so big
The size of a video is mostly its bitrate (how many bits are used per second) times its length. Phones and cameras record at high bitrates so that every frame stays sharp while you film. A one-minute 1080p clip from a phone is often well over 100 MB, and 4K is several times that. Most of those bits are not needed to watch the video on a screen, which is why a 50% smaller file often looks the same.
How much smaller
| Setting | Typical use | What changes |
|---|---|---|
| 30% smaller | Archive, keep quality | Hard to see a difference |
| 50% smaller | Share by message or email | Slightly softer in fast motion |
| 70% smaller | Long videos, slow connections | Visibly softer; good on a phone |
| Under N MB | A fixed upload limit | Bitrate, and if needed resolution, chosen to fit |
The fixed sizes are 8, 10, 25, 50 and 100 MB, and Under … MB lets you type any size. If a pass comes out a bit too big, it is run again at a lower bitrate, up to three times, so the file lands under the limit.
Resolution or bitrate?
For a small target, a lower resolution looks cleaner than the original size with very few bits, which turns blocky. The Resolution setting stays on Keep by default and is lowered only when the bitrate is too low for the frame. You can also choose 1080p, 720p or 480p yourself. A 4K phone video at 1080p is about a quarter of the pixels and still sharp on a laptop or phone screen.
Tips
- Phone videos are often recorded at a very high bitrate; 50% smaller usually looks the same.
- If a video is already small (for example downloaded from a social app), compressing again gains little.
- Cut what you don’t need first with Trim Video. A shorter video can keep a higher bitrate for the same size.