Why are my files so big? A practical guide to file sizes

Files get big for three reasons: resolution, bitrate, and format. Once you know which one is the culprit, shrinking is easy.

Videos

Resolution and bitrate are the drivers. 4K video is 4× the pixels of 1080p. The fix: compress (lower bitrate/CRF) or downscale. A 10-minute 4K clip can shrink from 1GB to under 100MB.

Images

Resolution and format. A 12MP phone photo is 4000×3000px — great for prints, overkill for the web. Resize to 1600px wide, then compress. Or convert to WebP for 30% more savings.

Audio

Bitrate and sample rate. WAV is uncompressed (huge); MP3 192kbps is 90% smaller. Convert between formats freely.

The golden rule

Match the file to the destination. Phone wallpaper? 1080px JPG. Email attachment? 1600px WebP. YouTube? 1080p MP4. Archive? Keep the original.