WordPress Image Sizes — Resize Featured Images (Free)

The sizes WordPress uses

Classic editor sizes: thumbnail 150×150, medium 300px, large 1024px. Most modern themes request 1200×675 featured images and 1920-wide hero images. Match the theme's registered size for pixel-perfect output.

Prepare a featured image

1. Open the Resize Image tool.
2. Drop your artwork or photo.
3. Resize to 1200×675 (16:9) for posts, or the theme's exact spec.
4. Export as JPG 80% and let WordPress generate the rest — usually hundreds of KB saved.

A pre-sized featured image also powers crisp link previews via the shared 1200×630 surface most SEO plugins use.

Skip the double-resize waste

Uploading a 5MB phone photo forces WordPress (and your CDN) to create 4-6 resized copies. Feeding an already-correct 1200px file means only the small thumbnails get generated — faster site, lighter media library.

WordPress resizing: the parts people miss

WordPress generates up to four registered sizes from every upload (thumbnail, medium, medium-large, large) plus the full original, and themes pick from that set for each placement. If your theme's content column renders at 800px wide but you upload 3000px originals, every visitor downloads an image the browser must shrink - and the original sits in the media library forever.

Practical numbers: 1600px wide for full-width heroes, 800px for in-content images matching a standard column, 400px for thumbnails you know will be small. Export the right size before uploading rather than trusting the editor, since generated sizes inherit the quality of the source and WordPress re-encodes JPEGs at 82% by default (editable, but most sites never touch it). Keep originals outside the library and upload only derivatives if page weight matters.