Newsletter Header Image Specs: Substack, Beehiiv, ConvertKit, and Beyond

Newsletter header images sit at the top of every email and the brand page. Get the dimensions wrong and either the platform crops your design or it stretches into pixelated nonsense. Each platform handles this differently, and the differences aren't documented in one place.

This guide is the platform-by-platform spec for newsletter header images in 2026, plus the merging workflow when you want to combine logo, tagline, and visual elements into a single header.

Substack

Substack uses two distinct image surfaces:

• Newsletter logo: 256 x 256 pixels (square), shown next to author name
• Cover image: 1080 x 1080 pixels (square), shown on the publication homepage and shared previews
• Featured image per post: 1500 x 1000 pixels (3:2 ratio), shown at the top of each post

The cover image carries the most weight. It appears in:

• The publication homepage
• Email preview when subscribers receive posts
• Social media when posts are shared
• Substack discovery feeds

For maximum impact, the cover image should:

• Have a clear focal point or text element
• Read at small thumbnail sizes (100 x 100 pixels)
• Match the publication's tone (playful, professional, niche)
• Avoid logos packed with detail that disappear at thumbnail size

For combining logo and tagline into one cover image, use our photo collage maker with a vertical layout.

Beehiiv

Beehiiv differs significantly from Substack:

• Logo: 512 x 512 pixels minimum (Beehiiv recommends 1024 x 1024 for retina)
• Banner image: 1500 x 500 pixels (3:1 ratio), wider than tall
• Featured image per post: 1200 x 630 pixels (Open Graph standard)
• Audience image: 1280 x 720 pixels for promotional surfaces

The banner ratio (3:1) is dramatically different from Substack's square cover. A design that works on Substack often looks crowded on Beehiiv's wide banner.

When migrating from Substack to Beehiiv, recreate the banner, don't just upload the same square cover. Use our horizontal image merge to combine elements across the wider canvas.

ConvertKit (now Kit)

ConvertKit's primary header image is for email templates:

• Email logo: 600 x 200 pixels max (3:1 ratio in email body)
• Landing page banner: 2000 x 400 pixels (5:1 ratio)
• Form image: 1500 x 600 pixels for embedded forms
• Profile image: 400 x 400 pixels (square)

Email logos benefit from horizontal layouts because they sit above text content. Vertical logos waste email real estate and force scrolling before the content begins.

For ConvertKit-specific email logo creation, the 3:1 ratio favors logo + tagline placed side by side. Our horizontal image merge handles this geometry directly.

Mailchimp

Mailchimp's header specs:

• Email header: 600 x 200 pixels recommended (most templates)
• Brand image: 200 x 200 pixels for sender thumbnail
• Hosted form image: 800 x 300 pixels
• Landing page hero: 1920 x 1080 pixels (16:9 ratio)

Mailchimp's older templates assume a 600 px wide email body. Modern templates support 800 px, but for compatibility across email clients (especially older Outlook versions), 600 px wide remains safest.

Buttondown

Buttondown is plain-text focused but supports some images:

• Newsletter cover image: 1200 x 630 pixels (Open Graph)
• Avatar: 400 x 400 pixels
• No banner image in default templates

Buttondown's minimal aesthetic means the cover image is the only major visual surface. Make it count.

Ghost

Ghost CMS for newsletters:

• Logo: 600 x 200 pixels recommended (transparent PNG)
• Cover image: 1200 x 800 pixels (3:2 ratio)
• Header image per post: 1200 x 800 pixels
• Author profile: 400 x 400 pixels

Ghost's email templates render the logo as the first visual element. Transparent backgrounds work cleanly because the email background may be light or dark.

Substack vs Beehiiv vs ConvertKit Comparison

If you publish on multiple platforms, design at the LARGEST resolution required, then export per platform with appropriate cropping. Our image cropper handles platform-specific aspect ratios.

Designing for Mobile

70% of newsletter opens happen on mobile. Headers display at:

• Mobile email: 375 px width on iPhone, 410 px on Android
• Mobile newsletter homepage: 320-410 px width
• Tablet: 768 px width

Test your header at 320 px wide. Can you read the publication name? Is the logo recognizable? If not, simplify.

For broader newsletter optimization, see social media image size guides which covers similar mobile-first principles.

File Format and Optimization

For email headers, file size affects:

• Email loading speed (slow image = subscriber leaves)
• Spam filter scoring (large images flagged)
• Mobile data usage (subscribers on cellular)

Recommended:

• Format: JPG for photos, PNG for logos with transparency
• Maximum file size: 200 KB for headers, 500 KB for banners
• Compression: lossy at 85% quality

Our image compressor reduces newsletter image file size by 50-70% with no visible quality difference.

Brand Consistency Across Platforms

If your newsletter exists on multiple platforms (Substack archive + Beehiiv current + Twitter promotion):

1. Design ONE master logo in vector format (SVG)
2. Export at multiple resolutions (256px, 512px, 1024px)
3. Create platform-specific banners using the same color palette
4. Use the same typography and visual style

For maintaining brand consistency, design the elements separately and combine using our overlay images tool to layer logo + tagline + decorative elements consistently.

Animated Headers

Some platforms support animated GIF headers. Pros and cons:

For email headers, assume 30-40% of subscribers won't see the animation (Outlook clients dominate corporate inboxes). Design so the first frame is the strongest single image, then animation adds polish.

Frequently Asked Questions

Should the publication name be in the header image?

Yes for cover images on the homepage (where the publication name appears below). For email headers, the name is in the From line, so the header can be purely visual.

What about retina displays?

Design at 2x the displayed size to ensure crisp rendering on high-DPI screens (most modern devices). For a 1080x1080 cover, design at 2160x2160 and let platforms downscale.

Can I use the same image across all platforms?

No. Each platform crops differently. A square Substack cover becomes a stretched mess on Beehiiv's 3:1 banner. Always design platform-specific versions.

How often should I update the header?

Publication homepage cover: yearly or with major brand updates. Email banner: monthly to quarterly to keep visual freshness. Logo: rarely, brand consistency matters more than novelty.

What about dark mode email clients?

Use logos with transparent backgrounds. Some clients invert images automatically. Test in Litmus or Email on Acid before sending to a large list.

The Bottom Line

For newsletter headers in 2026: design platform-specific versions, prioritize mobile readability, keep file size under 500 KB. Substack wants square, Beehiiv wants wide 3:1, ConvertKit wants horizontal email logos. Use our horizontal image merge, image cropper, and image compressor to handle the multi-platform export.

For more on email image optimization, see best image sizes social media 2025 and image formats explained.