The short version
- A good Substack header image size for a post is 1456×816 pixels, a landscape frame close to 16:9.
- The first image in a Substack post opens the email and usually becomes the post's thumbnail and social preview.
- Substack lets you set a separate social preview image in a post's settings when the header isn't right for sharing.
- Shared links crop the image to a slightly wider shape, so words and the subject belong in the centre of the header.
- Using one layout and look for every issue's header makes a newsletter recognisable in inboxes, feeds and the Substack app.
On this page
The Substack header image size to use for a post is 1456×816 pixels, a landscape frame close to 16:9. Placed at the top of a post, it opens the email, becomes the post's thumbnail on your publication's home page and in the Substack app, and is used as the preview image when the link is shared. Shared links and thumbnails crop it a little, so keep the headline and subject in the centre and let the background run to the edges.
Substack image sizes for a post
Size to design at
Ratio
Where it shows
Size to design at
Ratio
Where it shows
Size to design at
Ratio
Where it shows
Size to design at
Ratio
Where it shows
There's no benefit in uploading wider than 1456 pixels, and a much smaller image will look soft on large screens. If you're unsure whether people mean the post header or the banner at the top of every email, the second is your publication's wordmark or logo, set once in your publication settings.
Substack header 1456×816
1456 × 816
Link preview 1200×630
1200 × 630
Medium header 1400×788
1400 × 788
Email header 1200×600
1200 × 600
Where to keep words on a Substack header
When a post is shared, most networks show its preview image at about 1.91:1, a touch wider than the 1456×816 header, so about 25 pixels come off the top and bottom. Thumbnails on your home page and in the app can trim the sides too. Put words inside a central area with about 120 pixels of plain background on the left and right, and the header survives all of it.
The post header as it opens the email: issue number, title and one line of context.
The same post as a shared link preview. With the words centred, nothing important is lost in the crop.
How to set the header and social image on Substack
- 1
Add the header first
Insert your 1456×816 image as the first thing in the post, above the opening paragraph.
- 2
Write its alt text
Substack has an alt text option on each image. Describe what it shows in a sentence.
- 3
Open the post settings
Before publishing, open the settings for the post and find the social preview and thumbnail options.
- 4
Set a separate social image if needed
If the header is a photo that doesn't explain the post on its own, upload a version with the title on it for sharing.
- 5
Check the preview
Send a test email to yourself and paste the post link into a draft on another network to see both versions.
Header ideas that make a newsletter recognisable
Readers scan inboxes by look before they read a subject line. A newsletter whose every issue opens with the same layout, the same type and the same background family is recognised at a glance. Newsletter branding goes further on name, voice and colour; for headers, these are the patterns that work.
- Issue number and title. Simple, and it makes the archive feel like a body of work.
- A colour per section. If you publish an essay one week and a roundup the next, give each format its own colour inside one family.
- A pulled line. One sentence from the post, set large, works well for essays and on Notes.
- Nothing at all on the image. A beautiful background with no words is fine for the email, as long as you set a titled social image for sharing.
Avoid
- A different stock photo every week
- The full post title squeezed across the width
- Words near the edges, lost in shared links
- Tiny text that disappears in a phone inbox
Do
- One layout and background family for every issue
- A short title or issue number, large
- Words in the central area
- Type that still reads on a phone screen
Weekly headers are repetitive work, which is where consistency slips. With Gradiently Pro you can design the header once and use bulk create with a spreadsheet of issue numbers and titles to make a run of them in one go, each with the same layout. Your Mark moves its calmest area behind the title on every one, and the same issue can be resized in one step into a square for Notes or a LinkedIn newsletter cover.
If you also publish on Medium, compare the Medium image size, and see link preview images for how shared links are drawn on every network. Email specific layouts are covered in email header design.
Questions people ask
What size is a Substack header image?
Use 1456×816 pixels for a post header. It is close to 16:9 and stays sharp in the email, on the web and in the app.
How do I change the thumbnail on a Substack post?
Open the post's settings before publishing and set the thumbnail or social preview image there. By default Substack uses the first image in the post.
Why is my Substack image cropped when I share it?
Most networks show link previews at about 1.91:1, slightly wider than the header, so a little is trimmed from the top and bottom. Keep words in the centre.
Is the Substack header the same as the publication logo?
No. The post header is the image at the top of each post. The logo and wordmark are set once in your publication settings and appear on every issue.
Should my Substack header have text on it?
It helps when the post is shared, because the image travels without your subject line. A short title or issue number in the centre is enough; long titles become unreadable on phones.
Written by Gradiently
The team behind Gradiently, a design tool built around Marks: living gradients that make everything you design look like yours.
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