Compress Images for Substack — Keep Quality, Beat the Limit

Substack newsletter images are embedded in email and displayed on web. Images must be optimized for both email clients and web browsers, with email-safe formats prioritized. Use ImageSmith to compress your Substack images before sending — free, instant, and entirely in your browser. No account needed, no watermarks, no ads. Target under 10,000KB for best results on Substack.

Max File Size

10,000 KB

Recommended Format

JPEG

Dimensions

1200×675 for newsletter cover images

Substack Compression Tips

  • 1.Email subscribers see compressed images — pre-optimize for email quality
  • 2.Keep email-embedded images under 200KB for reliable delivery
  • 3.Use JPEG for photographs — Substack email clients do not support WebP
  • 4.Cover images display at 1200×675 in web and email previews

Compress by Format

Other Platform Optimizers

Substack Image Optimization FAQ