Why are video files so large?
Raw video is enormous — an uncompressed minute of 1080p footage can be several gigabytes. To make video files usable, they're encoded using codecs that throw away visual information your eyes won't notice. How aggressively they do that is what determines file size versus quality.
When people say they want to compress a video "without losing quality," what they usually mean is: make it smaller, but keep it looking good. The good news is there's a lot of room to compress most video before it starts looking noticeably worse.
Understanding CRF — the key setting
The main control for video compression quality is called CRF (Constant Rate Factor). It's a number that tells the encoder how much quality to preserve versus how small to make the file. Lower CRF = better quality, bigger file. Higher CRF = smaller file, more compression.
| CRF Value | Quality | Best For |
|---|---|---|
| 18–20 | Visually lossless | Archiving, master copies |
| 23–26 | High quality | Most sharing and streaming |
| 28–32 | Good quality | Social media, small file sizes |
| 35+ | Noticeable compression | Previews, rough cuts |
For most purposes — sharing with friends, uploading to a platform, or sending over email — a CRF of around 26–28 reduces file size dramatically with no visible quality loss to most viewers.
Which format should you compress to?
MP4 with H.264 encoding is the most compatible option. It plays everywhere — phones, TVs, browsers, social media — and compresses well. It's the right choice when compatibility matters.
WEBM with VP9 encoding gives better compression than MP4 at the same quality, making files even smaller. The tradeoff is slightly less universal compatibility — some older devices and apps don't support it. Great for web use.
If you're uploading to YouTube, Instagram, or TikTok, don't over-compress before uploading — these platforms re-encode your video anyway. Upload at higher quality (CRF 20–23) and let the platform handle the final compression.