WordPress automatic sizes

hard convention

WordPress (defaults)

150 / 300 / 768 / 1024 Horizontal format various

This is the set of sizes WordPress generates automatically when you upload a photo. Use 150 / 300 / 768 / 1024, so it looks right and loads fast.

This size is a hard convention: change it and something gets cropped or looks off.

See this photo everywhere

For whoever builds the site

WordPress auto-generates: thumbnail 150×150 (hard crop), medium max 300, medium_large max 768 wide, large max 1024. Themes assume these sizes. Site icon: square ≥512×512 PNG. Custom header: whatever your theme declares in the Customizer (no universal number).

Ratio: various
Desktop: 150 / 300 / 768 / 1024
Range: site icon ≥512×512

Official docs: WordPress.com (opens in a new tab) WordPress.org (opens in a new tab)