# Video compressor: shrink a video to a size limit, free, no upload

> Compress a video to the size you need in your browser. Pick a limit, and the tool works out the bitrate and frame size that fit, then writes an H.264 MP4. Nothing is uploaded.

URL: https://cutfac.com/tools/video-compressor  
Last updated: 2026-10-28  
Language: [한국어](https://cutfac.com/ko/tools/video-compressor)

Drop in a video, pick the size it has to fit, and get an MP4 under it. The tool works out the bitrate and frame size, and the video never leaves your browser.

Runs in your browser. Nothing is uploaded.

## How to use it

1. **Add the video.** Drop it in. The tool shows its frame size, length and file size.
2. **Pick the limit.** Tap a size or type your own. The line below shows the bitrate and frame size it will use.
3. **Compress and download.** Play the result to check it, then download the MP4.

## How the size is worked out

A file's size is its bitrate times its length. The tool takes the limit, keeps a tenth back because encoders land near the bitrate rather than on it, sets aside 128 kbps for the sound, and spreads the rest over the video's length.

When that leaves too few bits for the frame, the picture turns to blocks. So the tool also steps the frame down, 1080p to 720p and so on, until the bitrate is enough for it. A smaller sharp picture looks better than a large blocky one.

## Getting a better result

Length is what matters most. Trimming a video to the part you need gives every second more bits, which shows more than any setting.

If the result comes out over the limit, pick the next size down and compress again. A video already under the limit doesn't need compressing.

## With ffmpeg

FFmpeg's guide suggests two passes when you're aiming at a file size: the first studies the video, the second encodes it. Set -b:v to the video bitrate the tool shows:

- ffmpeg -y -i input.mp4 -c:v libx264 -b:v 2600k -pass 1 -an -f null /dev/null && ffmpeg -i input.mp4 -c:v libx264 -b:v 2600k -pass 2 -c:a aac -b:a 128k output.mp4

## Sources

- [FFmpeg Wiki: H.264 video encoding guide](https://trac.ffmpeg.org/wiki/Encode/H.264)
- [Gmail Help: Attachment size limits](https://support.google.com/mail/answer/6584)

## Questions

### Is my video uploaded?

No. The video is decoded and the MP4 is encoded in your browser. Nothing is sent anywhere.

### What size should I pick for email?

25 MB for personal Gmail, Google's limit for attachments. Other mail services set their own, often lower.

### Why is my compressed video smaller in pixels?

At a tight limit there aren't enough bits for the full frame, so the tool steps it down to keep the picture clean. A bigger limit keeps more of it.

### How long does it take?

Every frame is decoded and encoded again, so it depends on the video's length and your computer. Keep the tab open until it finishes.

### Which videos can it read?

Whatever your browser can decode: MP4, MOV, WebM and most MKV files. The result is always an H.264 MP4 with AAC sound.