- Logo: At least 256 x 256 px with a transparent background.
- Email banners: Recommended 1100 x 220 px with a transparent background, but could be taller.
- Cover image: At least 600 x 600 px.
- Social / post preview image: We recommend at least 1456 x 1048 px, but 420 x 300 px is the minimum. 14:10 is the aspect ratio for the preview images.
- Full-width images: The maximum aspect ratio is 1:1 for height — taller images will be automatically cropped to 1:1.
If some images with faces are being cut off in your post thumbnails (social preview images), try enabling smart cropping on your publication. Head to the Website section on your publication's Settings page and select "Smart cropping" next to where it says "Image cropping for post thumbnails".
To get more tips from our Substack design team, check out our design guide here.