Substack Image Sizes: Header, Logo & Post Images (2026)

The Substack header image appears at the very top of your publication homepage and in the navigation area. It functions like a banner — wide and relatively narrow. The recommended dimensions are 1100 x 220 pixels (a 5:1 ratio).

On desktop, this displays at full width across the content area. On mobile, the image is scaled down and the left and right edges can get slightly cropped depending on the device width. The practical takeaway: keep your most important content — publication name, illustration, branding elements — in the center 60% of the image. Treat the outer 20% on each side as a bleed zone that might be clipped.

Avoid placing small text in your header. At mobile sizes, anything below about 24pt (in the original image) becomes illegible. A simple illustration, pattern, or bold wordmark works far better than a detailed composition.

Your Substack logo appears in the top navigation bar, in email headers, and as the favicon-adjacent identifier across the platform. Substack recommends a square image — 256 x 256 pixels minimum, though uploading at 512 x 512 gives better results on high-density displays.

The logo is displayed at roughly 26-40 pixels depending on context. That means fine details, thin strokes, and small text will be completely lost. Design your Substack logo the way you would design an app icon: bold shapes, high contrast, and no reliance on legible text. A single letter, a simple mark, or a bold monogram works best.

Use PNG with a transparent background if your logo is a mark or icon. Use JPG if it is a full-frame photo or illustration with no transparency needed.

Substack's content column is 728 pixels wide on desktop. But because the platform serves images at 2x resolution for Retina and high-DPI screens, your inline post images should be 1456 pixels wide. Height is flexible — use whatever aspect ratio makes sense for the image.

If you upload images narrower than 1456px, they will still display fine on standard screens, but they will look noticeably soft on MacBooks, iPhones, and other high-density displays — which is a large portion of the Substack audience. Newsletter readers tend to skew toward Apple devices, so Retina sharpness is worth the effort.

For file size, aim for 150-400 KB per inline image. Substack does compress images on upload, but starting with a well-optimized file gives you more control over the final quality. Overly large files also slow down email load times for readers who receive posts in their inbox.

When a Substack post is shared on social media or previewed in email clients, the post's cover image (the first image in the post, or the one you set as the social preview) is used as the Open Graph image. For best results across Twitter/X, Facebook, and LinkedIn, use a 1200 x 630 image as your post's lead visual.

If you do not set a specific social image, Substack will use your header image or logo, which rarely looks good in a social card format. Take the extra 30 seconds to set a dedicated cover image for every post — it makes a measurable difference in click-through rates from social shares.

The best-looking Substack publications commit to a visual system. Pick one or two aspect ratios for your post images and stick with them. A 16:9 landscape works well for cover images, while 4:3 or 3:2 works well for in-post photography. Using consistent ratios makes your archive page look intentional rather than haphazard.

If you use charts, diagrams, or screenshots, give them a consistent background color and padding. Raw screenshots with varying window chrome look messy. A simple border or drop shadow on a consistent background immediately elevates the presentation.

Batch process your images before uploading. Resize to 1456px wide, compress to your target file size, and export. This takes minutes with the right workflow and saves your readers from unnecessarily heavy pages.