Substack Image Sizes: Header, Post, and Article Dimensions (2026)

Substack cover image size — 1456 x 816

The image at the top of a Substack article is not a separate upload slot. You drop it into the draft like any other image and choose Set full widthfrom the three-dot menu, which is why Substack publishes no dimension for it. The width that matters is its own: Substack’s image CDN builds each post image at 424, 848, 1272 and 1456 pixels wide and stops there, so 1456 is the largest copy a reader can ever be served.

• Uploading wider than 1456 buys nothing. The CDN caps the variant it builds, so a 3000 px master is downscaled to the same 1456 px file every reader gets. It only costs you upload time.
• Uploading narrower than 1456 does cost you. The c_limit setting means Substack shrinks but never enlarges: a 728 px upload stays 728 px and looks soft on a retina screen, which is the usual reason a Substack cover looks blurry.
• 16:9 is a choice, not a rule. Any ratio up to 1:1 renders untouched. 1456 x 816 is simply the shape that fills the column without pushing the first paragraph off the screen.
• The cover is not automatically the thumbnail. Substack picks a preview image separately — see the email thumbnail section before you assume the inbox shows the same crop.

Resize an image to 1456x816 → Pick Substack, then the Newsletter Header preset.

Substack post header image — 1100 x 220

“Header” means three different assets on Substack, and only one of them has a published size. The email header banner — the strip that sits above your post title in the inbox — is 1100 x 220 PNG. It appears in emails only, never on the web post, which is why writers hunting for it in the post editor never find it.

If you searched for a header size and this is not the asset you meant, it is one of these two:

• The image at the top of the article — that is the cover image, 1456 x 816. It lives in the post body, not in any settings page.
• The logo in your publication’s header bar and email sender block — that is 256 x 256, transparent background.
• A transparent banner can vanish in dark mode. Mail clients recolor the background behind an image without touching its pixels, so dark artwork on transparency disappears against an inverted inbox. Test in dark mode, or keep the mark light. Our email header image sizes guide compares how each platform handles this.

Substack email thumbnail — 1200 x 630 minimum, shown at 14:10

The thumbnail is the social preview image, and Substack reuses it everywhere a post is summarised rather than read: the inbox digest, the app feed, your archive, and social cards. Substack recommends at least 1200 x 630 for it — and separately states that 14:10 is the ratio previews are shown at. Those two numbers do not describe the same rectangle, which is where subjects lose their heads.

• Design at 1456 x 1040 and the crop problem disappears. It is already 14:10, so the preview shows the whole frame, and it clears the 1200 x 630 minimum with room to spare.
• Or keep the subject centred. A 1200 x 630 export loses about 159 px from each edge in the preview. Text set hard against the left or right is exactly what gets cut.
• Turn on smart cropping if faces keep getting clipped. Dashboard → Website editor → Home page → Cropping, then choose Center or Smart. Smart targets the most interesting part of the image instead of the geometric middle.
• Substack falls back to a body image if you set nothing. That is fine when your cover is a photo and fatal when the first image in the post is a chart or a screenshot — set the preview deliberately on posts that matter.

Resize an image for the preview → Pick Substack, then Social / Email Thumbnail.

Substack profile picture and logo — 256 x 256

Substack publishes one square minimum, and it is for the publication logo: at least 256 x 256 with a transparent background. The author profile photo has no published figure, so use the same square — it is rendered at the same small sizes and cropped to a circle in bylines, comments and the app.

• A wordmark is not a logo here. At 256 px cropped to a circle, a five-word publication name is unreadable. Use a monogram or a single mark and put the full name in the publication title.
• Transparent PNG cuts both ways. It looks right in Substack’s own chrome and can vanish in a dark-mode inbox. If your mark is dark, give it a light background rather than transparency.
• Headshots need to be tight. A circle at byline size shows a head, not a scene. Crop to the face before uploading rather than letting the circle do it.

Substack podcast cover art — square, 1400 to 3000 px

Substack asks for a square image at least 1400 px wide when you create a podcast, and notes that for Apple Podcasts an episode image should be greater than 1400 x 1400 and less than 3000 x 3000. That upper bound is the reason to stop short of the 3000 x 3000 that general podcast guides recommend — 2048 x 2048 sits comfortably inside both limits.

• Upload your own art or Substack picks for you. Left alone it falls back through episode art, the social preview, an image from the post body, then a default microphone graphic — a chain that produces inconsistent tiles across players.
• Design for a thumbnail. Podcast apps render cover art small in lists. One idea, high contrast, a short title; a subtitle set at 2048 px will be illegible at 200 px.
• Imported shows do not bring their art. Substack states podcast artwork does not transfer when you import a podcast — re-upload it.

Resize an image to 2048x2048 → Pick Substack, then Podcast Cover Art.

Article image dimensions inside the post body

Images in the body of an article follow one width and one ratio rule. The width is the same 1456 px ceiling as the cover. The ratio rule is Substack’s only published constraint on in-post images: a full-width image can be no taller than 1:1, and anything taller is automatically cropped square.

• Tall screenshots are the trap. A phone screenshot is taller than 1:1, so setting it full width crops it square and the bottom of the screen is gone. Leave it at the default inline width, or crop it yourself first.
• Gmail clips long emails at about 102KB of message content. That is the total, not per image — a heavy GIF near the top can push the rest of the post behind a “View entire message” link. Substack publishes no image size limit, but the inbox effectively does.
• Animated GIFs ship every frame to every subscriber. They are supported, and they are the single easiest way to blow past that clipping threshold. One per post, short loop.
• Send yourself a test email before publishing. The web post and the inbox copy are rendered by different engines; sharpness, dark mode and image placement all differ.