CSS function · data last changed 10 Nov 2026
clamp in email clients
Works in 6 of 21. Not supported in Outlook 365, Outlook (New), Outlook Classic and 8 more. Partial in Gmail Android, Gmail iOS and Samsung Mail. Untested in Superhuman.
Your reader in Outlook Classic sees the email without clamp, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
Provide a fixed pixel fallback declaration before clamp() so non-supporting clients still receive a sensible value. Keep the clamp() range conservative in email, extreme min/max values render unpredictably across mobile clients.
There is no drop-in fix for clamp in Outlook Classic. Design so the email still reads without it.
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clamp is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook 365 | Not supported |
| Outlook (New) | Not supported |
| Outlook Classic | Not supported |
| Outlook iOS | Not supported |
| Outlook Android | Not supported |
| Outlook for Mac | Not supported |
| Yahoo Mail | Not supported |
| Yahoo Mail Android | Not supported |
| Yahoo Mail iOS | Not supported |
| AOL Mail | Not supported |
| Fastmail | Not supported |
| Gmail Android | Partial See caveat 1 |
| Gmail iOS | Partial See caveat 1 |
| Samsung Mail | Partial See caveat 2 |
| Superhuman | Untested |
Works in 6: Gmail, Apple Mail, Apple Mail iOS and 3 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
Caveats (2)
- 1. Gmail Android, Gmail iOS: Partial. Not supported with non Google accounts.
- 2. Samsung Mail: Partial. Not supported with Microsoft accounts.
Caveats as recorded by caniemail (MIT), one entry per wording.
How clamp behaves
The clamp() function locks a value between a minimum and maximum, with a preferred middle value. It is widely used in modern responsive web design but has limited email support, Apple Mail and modern Gmail honor it, while Outlook Classic ignores it entirely.
- Outlook Classic ignores clamp() and uses the original CSS keyword fallback.
- Gmail supports clamp() in recent Chromium versions; Gmail mobile is more conservative.
- Browser-style fluid typography expectations don't always translate to email viewports.
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