CSS property · data last changed 10 Nov 2026
unit-vw in email clients
Works in 18 of 21. Not supported in Outlook Classic and Fastmail. Untested in Superhuman.
Your reader in Outlook Classic sees the email without unit-vw, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
There is no drop-in fix for unit-vw in Outlook Classic. Design so the email still reads without it.
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unit-vw 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 | Not supported |
| Fastmail | Not supported |
| Superhuman | Untested |
Works in 18: Gmail, Gmail Android, Gmail iOS and 15 more. Show all
| Client | Support |
|---|---|
| Gmail | Works See caveat 1 |
| Gmail Android | Works |
| Gmail iOS | Works |
| Outlook 365 | Works See caveat 1 |
| Outlook (New) | Works See caveat 1 |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works See caveat 1 |
| Yahoo Mail Android | Works |
| Yahoo Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
| AOL Mail | Works See caveat 1 |
Caveats (1)
- 1. Gmail, Outlook 365, Outlook (New), Yahoo Mail, AOL Mail: The HTML of the email message is embedded directly on the webmail (not in an <iframe>) and may not fill the full viewport's width. In this case, the vw values are relevant to the viewport (browser window) not the email message.
Caveats as recorded by caniemail (MIT), one entry per wording.
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