Making a Video Small Enough to Send
Phone video is enormous. A minute of 4K at 60 frames per second can exceed 400 MB, which will not attach to an email, will not fit a messaging app’s limit, and takes an age to upload anywhere. Most of that size is resolution and frame rate nobody will notice on the screen the video will actually be watched on.
This compressor re-encodes video in your browser, trading resolution and bitrate against file size, without the recording being uploaded anywhere.
How to Compress a Video
Resolution does more for file size than any other setting, and it is usually the one with the least visible cost.
- Drop the video onto the box above. MP4, MOV, M4V, WebM and MKV are accepted.
- Choose a quality preset. Lower presets reduce both resolution and bitrate, which is what produces the large savings.
- Consider where the video will be watched. Anything viewed on a phone gains nothing from 4K, and 1080p is usually indistinguishable on that screen.
- Start the compression. Re-encoding is processor-intensive, so a long video takes real time, a few minutes of footage can take a few minutes to process.
- Compare the resulting size against the original before downloading.
- Download the compressed file. Your original is untouched, so you can try a different preset if the result is too aggressive.
Where the File Size Actually Goes
Video size is driven by three things: resolution, frame rate and bitrate. Resolution has the largest effect because pixel count scales with area, dropping from 4K to 1080p removes three quarters of the pixels, and that is before any change to the bitrate. Frame rate is linear, so halving 60 fps to 30 fps roughly halves the data, though motion becomes less smooth.
Bitrate is the direct control over quality within a given resolution, and it is where compression artefacts appear if pushed too far. Blocking in dark scenes and smearing on fast motion are the usual signs. The practical approach is to reduce resolution first, since a 1080p file at a healthy bitrate looks considerably better than a 4K file starved of one.
Resolution and Typical Bitrate
Approximate file size for one minute of footage at a reasonable bitrate for each resolution.
| Resolution | Pixels | Typical bitrate | Size per minute |
|---|---|---|---|
| 4K (2160p) | 8.3 M | 35–45 Mbps | ~300 MB |
| 1440p | 3.7 M | 16 Mbps | ~120 MB |
| 1080p | 2.1 M | 8 Mbps | ~60 MB |
| 720p | 0.9 M | 5 Mbps | ~37 MB |
| 480p | 0.4 M | 2.5 Mbps | ~19 MB |
Going from 4K to 1080p cuts the file by roughly eighty per cent, and on a phone screen the difference is essentially invisible. That is almost always the first thing to try when a video is too large to send.
Time, Heat and Practical Limits
Re-encoding is genuinely demanding work. The browser has to decode every frame and encode it again, so processing time scales with length and resolution, and a laptop will get warm doing it. Leave the tab in the foreground while it runs, since browsers throttle background tabs and that will slow it down considerably.
Compression is also generational, as with images and audio. A video already compressed for streaming has lost detail permanently, and re-encoding it degrades it further. When you have the original recording, compress from that rather than from a copy that has already been through the process once.