CSS property · data last changed 10 Nov 2026
letter-spacing in email clients
Works in 20 of 21. Partial in Outlook Classic.
Your reader in Outlook Classic may not see letter-spacing the way you wrote it, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
Always declare letter-spacing using explicit pixel values (e.g., letter-spacing: 1px or letter-spacing: 2px) rather than em or rem units. Avoid negative letter-spacing in email copy to prevent clipping and overlapping characters in Microsoft Word-based Outlook clients.
- Partial. Big negative values are rendered differently from CSS standards.
- Buggy. Values set in
emare smaller than the expected render in CSS. See #192.
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letter-spacing is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook Classic | Partial See caveat 1 |
Works in 20: Gmail, Gmail Android, Gmail iOS and 17 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Gmail Android | Works |
| Gmail iOS | Works |
| Outlook 365 | Works |
| Outlook (New) | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works |
| Yahoo Mail Android | Works |
| Yahoo Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
| AOL Mail | Works |
| Fastmail | Works |
| Superhuman | Works |
How letter-spacing behaves
The letter-spacing property adjusts the horizontal tracking between characters of text. It is commonly employed in email typography to add elegance to uppercase headings, eyebrow categories, and call-to-action buttons. While letter-spacing enjoys widespread baseline support across webmail and mobile clients, Outlook Classic introduces rendering quirks that require careful unit selection.
- Gmail (Web, iOS, and Android), Apple Mail, and Yahoo Mail support letter-spacing smoothly with standard CSS behavior.
- Outlook Classic (Word engine) exhibits mathematical rounding bugs when letter-spacing is declared in em units, rendering characters significantly tighter than intended.
- Large negative letter-spacing values can cause text characters to overlap illegibly in Outlook Classic.
Questions
Why does letter-spacing look too small in Outlook Classic?
Outlook Classic miscalculates relative em units for letter spacing. Always use explicit pixel units (px) for letter-spacing declarations in email.
Does Gmail support letter-spacing?
Yes. Gmail supports letter-spacing fully, both when declared in inline style attributes and inside <style> blocks.
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