Compress a video online

How to compress a video

Drop an MP4, MOV, MKV, WebM, AVI or M4V above. Move the Compression (CRF) slider and choose a maximum resolution if the source is bigger than you need. Press Convert. The video is re-encoded to H.264 with AAC audio at 160 kbps, and the result keeps the original's aspect ratio. The queue shows the size before and after, so you can try again with other settings if it is still too big.

What CRF means

CRF stands for Constant Rate Factor. Instead of a fixed bitrate, the encoder keeps a steady visual quality and spends bits where the picture needs them. The slider runs from 18 to 40. Each step of about 6 roughly halves or doubles the file size. 18 looks nearly identical to most sources, 28, the default, is a good balance, and 34 to 40 is for small previews where size matters most.

Settings for common size limits

Pick a starting point for where the video is going:

• Email with a 25 MB limit: CRF 30 to 32 with a 720p cap for clips up to a couple of minutes.
• Discord's free upload limit: CRF 32 with a 720p cap, and trim the clip first.
• WhatsApp: CRF 28 with a 720p cap, since WhatsApp compresses again on upload.
• Keeping a smaller archive copy: CRF 23 to 26 at the original resolution.

Why the resolution cap matters

Phones record 4K by default, which most people watch on a phone screen anyway. Capping at 1080p cuts the pixel count to a quarter, and 720p cuts it to about a ninth. That shrinks the file more than any CRF change and keeps the picture sharp on phones and laptops. The cap never enlarges a smaller video.

Before you start

Input: MP4, MOV, MKV, WEBM, AVI, and M4V. Output: MP4. The settings appear before anything runs, so you can check them first. Your original file is never changed.

Video work uses a lot of memory and CPU. Try a short clip first and check that the sound and playback work. On a phone, split large batches into smaller ones.

Keep the original until you have opened and checked the result. The work happens in this browser tab, so the size you can handle depends on your device's memory, your browser and the file itself.

How to compress a video online

1. Drop the video you want to compress.
2. Set the compression slider and, if you want, a maximum resolution.
3. Press Convert and download the smaller MP4.