The newsletter is the brand's longest-form owned channel. It arrives in an inbox as a letter, not a feed post, and gets read at whatever width the reader's client allows. Substack is the current platform, and a switch changes the settings rather than the guidance. The studio team owns it.
Regulations
These come from two places: Substack's published dimensions, and what mail clients render faithfully. Neither is ours to negotiate.
| Format | Size / ratio | Safe area | File format | Max weight | Notes |
|---|---|---|---|---|---|
| Publication logo | 256×256 minimum · 1:1 | square crop, centre the mark | PNG transparent, or JPG | not published | avatar logo variant |
| Wordmark | 1344×256 minimum · 21:4 | n/a | PNG transparent | not published | no existing lockup fits 21:4, so the export is requested from design |
| Header banner | 1100×220 · 5:1 | keep content centred | PNG transparent, or JPG | keep light, it loads in email | tops every sent email |
| Cover image | 600×600 minimum · 1:1 | n/a | PNG/JPG | not published | the publication's directory card |
| Post feature image | 1456×1048 | focal point centred | PNG/JPG | roughly 150 KB working target | doubles as the post's social preview |
| Inline images | 1600px wide upload, renders at 800px | body crops anything taller than square | PNG/JPG/GIF | keep light | 2× upload keeps retina sharp |
Substack publishes the dimensions but no hard file-size caps. The weights above are deliverability targets rather than platform limits, and they matter because heavy images are the difference between a newsletter that opens and one that gets clipped mid-scroll. Verified 2026-07-05.
Standards
- Logo: the square publication logo takes the avatar variant. Variants: 4.1 Logo
- Colour: the header banner and designed imagery carry the brand palette. Body text stays on the platform's reading defaults rather than fighting them: 4.2 Colour
- Type: designed assets, meaning the header and feature images, use the brand type roles. Body copy renders in the platform's email-safe stack, the same constraint the Email Signature works under: 4.3 Typography
- Every post ships with a feature image. It doubles as the social preview, so a post without one hands the platform the decision about how the brand looks when it is shared.
- Design inline images landscape or square. The body crops anything taller, so a portrait composition loses its top and bottom with nothing to warn you.
- Voice: a newsletter is read, not scrolled past. It earns the space for full arguments, in the same register as everything else: 3.3 How We Communicate. Subject lines follow the headline rule, so an argument rather than a label.
Formats
Design is building the header-banner and feature-image blanks at spec size, plus the wide wordmark export. Each frame below holds its format at the exact ratio until the template lands.
Header banner, 1100×220 (5:1)
Post feature image, 1456×1048
Wide wordmark, 1344×256 (21:4)
Tools
- Image Placeholder, draft-stage imagery at exact header and feature dimensions
No newsletter-specific tool exists yet. A weight check on a composed post, run before the test send, is the obvious first one, because clipping is invisible to the sender. Request it when a letter gets clipped.
Don't
Don't publish without a feature image
The feature image is the social preview. Without one, every share of the post renders as a bare link. The platform decides how the brand looks.
Don't send heavy images
Mail clients clip long, heavy emails. An oversized inline image can cut the letter off before the sign-off, and the reader never knows.
Don't rely on tall imagery
The body crops anything taller than square. A portrait composition loses its top and bottom. Design inline images landscape or square.
Checklist
- Feature image present at 1456×1048, focal point centred
- Inline images landscape or square, uploaded at 2×, kept light
- Logo and wordmark slots carry the correct variants
- Subject line is an argument, not a label; body passes the voice check
- Test send checked in a real mail client before publishing