Compress Images for Substack
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 size
10,000 KB
Format
JPEG
Size
1200×675 for newsletter cover images
- 1Email subscribers see compressed images — pre-optimize for email quality
- 2Keep email-embedded images under 200KB for reliable delivery
- 3Use JPEG for photographs — Substack email clients do not support WebP
- 4Cover images display at 1200×675 in web and email previews