Email Specs
Email Image Specs
Email images fail in ways web images do not: blocked by default, resized by Outlook, and stripped of context when they do not load. I design assuming the image is off and the alt text is all the reader sees, then treat everything visual as an upgrade.
| Item | Recommendation | Reason |
|---|---|---|
| Email body width | 600 to 640 pixels | Fits desktop preview panes |
| Full width image | 1200 pixels wide, displayed at 600 | Retina sharpness |
| Format | JPG for photos, PNG for flat graphics | Best size to quality trade |
| Animated content | GIF | Outlook shows the first frame only |
| Modern formats | Avoid WebP and AVIF as the only source | Inconsistent client support |
| Total email weight | Under about 1 MB, ideally far less | Gmail clips long messages |
| Attribute | Rule | Why |
|---|---|---|
| width | Set in HTML attribute and inline CSS | Outlook ignores some CSS |
| height | Set auto in CSS, avoid fixed height | Prevents distortion on scaling |
| alt | Always populated and meaningful | Rendered when images are blocked |
| display | Set display block on images | Removes gaps under images |
| style | Inline, not in a stylesheet | Some clients strip head styles |
Notes
Many recipients see images off on first open, so the email has to work as text. That means never putting the offer, the price or the call to action inside an image only, and writing alt text that carries the message rather than describing the picture. A styled HTML button beats an image button for the same reason.
Gmail clips messages that exceed roughly 102 KB of HTML, which hides everything below the cut behind a View entire message link, including your unsubscribe footer. Keep the markup lean, avoid duplicated inline styles from drag and drop builders, and test the raw HTML size, not the image weight.
Serve images at two times the display width and set the display width explicitly. Retina screens are the majority of opens and an unscaled image looks soft in a way that reads as low quality even to readers who could not name why.
Client rendering behaviour changes as Outlook, Gmail and Apple Mail update, including image proxying and privacy features that affect tracking pixels. Verify current behaviour with real client testing rather than relying on a spec sheet alone.
Frequently asked questions
Can I use a single image for the whole email?
You can, and it will underperform and look like spam to filters. Split it into text and images so the message survives image blocking and remains accessible.
Do animated GIFs work?
In most clients yes, but Outlook on Windows shows only the first frame. Make the first frame a complete message and treat the animation as a bonus.
What is the safe email width?
600 pixels is the long standing safe content width. Some brands go to 640 without problems, but 600 remains the value I use when reliability matters more than presence.
Official sources
Platforms change specifications without notice. Check the primary documentation before a launch that depends on an exact value.
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