Video Compressor

How to Compress a Video Online

1. Drop your video file onto the upload area. MP4, WebM, MOV and MKV up to 500 MB are accepted.
2. Pick a compression preset: higher quality (CRF 23, larger file), balanced (CRF 28, default), or smallest size (CRF 32, more visible artifacts).
3. Press Compress. The file uploads to our EU servers, FFmpeg re-encodes it with H.264 + AAC, and you download the smaller MP4.
4. Both the original and the result are auto-deleted within 15 minutes. We do not log, store or analyse the content.

How CRF affects file size

CRF (Constant Rate Factor) is the H.264 quality knob. Lower CRF means more bits per pixel, which means a larger file at higher visual quality. CRF 18 is "visually lossless", CRF 23 is the libx264 default for archival quality, CRF 28 cuts file size by roughly half compared to 23 with quality drop visible only on careful comparison, and CRF 32 is suitable for thumbnails or chat attachments where size matters more than detail.

The compressor uses the fast encoder preset, which is the sweet spot of speed vs efficiency. medium would be ~10 percent smaller for the same CRF but takes 2x longer; veryfast is faster but ~10 percent larger. Most users do not notice the difference for short clips, so we lock fast as the default.

When to compress before sharing

• WhatsApp, Telegram, Discord and email attachments cap files between 25 and 200 MB depending on the channel - compressing a 4K phone clip down to ~30 MB is usually enough.
• Embedding a demo into a Notion page, Slack thread or GitHub issue: smaller files load faster on mobile.
• Saving disk space on a phone or laptop: a 30-second screen recording can drop from 80 MB to 10 MB with no visible change for most viewers.

Why H.264 and MP4

The compressor always outputs MP4 with H.264 video and AAC audio because that combination has the widest "open and just play" success rate of any modern format. iOS, Android, every desktop browser, social platforms, messaging apps and even decade-old hardware decode it without a plugin or conversion step. Newer codecs like H.265, VP9 and AV1 are more efficient at the same quality - they can hit a similar size at a lower bitrate - but their playback support is still patchy: Safari only added partial WebM handling recently, and many editing apps still refuse to import VP9. Choosing H.264 trades a little compression efficiency for the guarantee that whoever you send the file to can actually watch it. That is why a WebM upload comes back as MP4: the tool standardises on the format least likely to fail downstream.

What actually shrinks, and what does not

How much a video compresses depends almost entirely on how much redundant data is in the source. A high-bitrate phone or camera clip recorded at 50-80 Mbps carries far more information than the screen needs, so CRF 28 can shave it 5-10x with no perceptible loss. A clip that was already compressed - a YouTube download, a re-shared social video, a Zoom export - has had most of its redundancy stripped, so a second pass might only trim 30-50 percent and start to show artefacts, because each lossy re-encode compounds the previous one. Screen recordings sit at the favourable extreme: large flat regions compress dramatically, which is why an 80 MB capture can collapse to 10 MB. The practical rule is to compress from the original capture when you can, and treat a download or forwarded file as a worst case.

Compress, convert, or trim first

Compression is the right tool when the video is the right length and resolution but simply too large to send. If the file is large mainly because it is long, trimming the parts you do not need with the video trimmer first gives a far smaller result than compression alone. If you need a different container or codec rather than a smaller size, the video converter handles format changes. And for a short, silent moment in a chat or doc, turning it into an animated GIF can be lighter still. Reaching for the right tool first often beats compressing harder.

Privacy, limits and the equivalent command

Accepted inputs are MP4, WebM, MOV and MKV up to 500 MB per upload. The file is sent over HTTPS to our EU server, FFmpeg re-encodes it, and the result is returned through a signed, time-limited URL; both the upload and the output are deleted within 15 minutes, and the link expires with them. The content is never logged, analysed or fed to any model. Encoding runs roughly in real time - a 60-second clip takes about a minute plus upload, with 4K and high-frame-rate footage two to three times longer - and a job past 10 minutes is stopped. For larger files or batch work, run it locally: ffmpeg -i input -c:v libx264 -preset fast -crf 28 -c:a aac -b:a 128k output.mp4.