unit-vh
CSS property · 16 supported, 1 partial, 3 unsupported across 21 clients
16 of 21 email clients render unit-vh fully (Sep 2, 2026 data); it breaks outright in Outlook (New), Outlook Classic, Fastmail.
- 6/7 webmail, 3/6 desktop, 7/8 mobile clients support unit-vh fully.
- Unsupported in Outlook (New), Outlook Classic, Fastmail.
- Partial in Apple Mail iOS, behavior differs from browsers, test before relying on it.
- Outlook Classic (Word engine, supported to at least 2029) does not fully support unit-vh, and its replacement changes little here; see the deprecation diff.
- Across all clients, only 6 of 298 tracked HTML/CSS features render identically everywhere.
Source: caniemail.com (MIT), via the Emailens engine. Last tested upstream Oct 1, 2023, synced by Emailens Sep 2, 2026.
Client Support
| Client | Category | Engine | Support |
|---|---|---|---|
| Gmail | webmail | Gmail Web | Supported |
| Gmail Android | mobile | Gmail Mobile | Supported |
| Gmail iOS | mobile | Gmail Mobile | Supported |
| Outlook 365 | webmail | Outlook Web | Supported |
| Outlook (New) | desktop | Outlook Web | Unsupported |
| Outlook Classic | desktop | Microsoft Word | Unsupported |
| Outlook iOS | mobile | Outlook Mobile | Supported |
| Outlook Android | mobile | Outlook Mobile | Supported |
| Outlook for Mac | desktop | WebKit | Supported |
| Apple Mail | desktop | WebKit | Supported |
| Apple Mail iOS | mobile | WebKit | PartialSee caveat 1 |
| Yahoo Mail | webmail | Yahoo | Supported |
| Yahoo Mail Android | mobile | Yahoo | Supported |
| Yahoo Mail iOS | mobile | Yahoo | Supported |
| Samsung Mail | mobile | Samsung | Supported |
| Thunderbird | desktop | Gecko | Supported |
| HEY Mail | webmail | WebKit | Supported |
| Proton Mail | webmail | Proton | Supported |
| AOL Mail | webmail | AOL | Supported |
| Fastmail | webmail | Fastmail | Unsupported |
| Superhuman | desktop | Blink | Unknown |
Documented caveats (1)
- 1.Apple Mail iOS: Buggy. Value resolves to zero
Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.
Client-by-client behaviour for unit-vh
Fully supports unit-vh (16): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, AOL Mail.
Partial support (1): Apple Mail iOS. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.
No support (3): Outlook (New), Outlook Classic, Fastmail. Plan fallbacks for these clients before relying on unit-vh in production sends.
Behaviour unverified in: Superhuman.
Fixes & Workarounds
Outlook (New)
Unsupported"unit-vh" is not supported in this email client.
Outlook Classic
Unsupported"unit-vh" is not supported in this email client.
Fastmail
Unsupported"unit-vh" is not supported in this email client.
Apple Mail iOS
Partial"unit-vh" is not supported in this email client.
Related Features
Check your own HTML for unit-vh
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your unit-vh layout across 21 email clients
Preview rendering, catch CSS issues, and see how unit-vh displays across Outlook, Gmail, and Apple Mail. Free, no account needed.
Instant live preview · No signup required · 21 email engines
Last tested upstream: · Last synced by Emailens:
caniemail.com (MIT) records Oct 1, 2023 as the last time unit-vh was tested in a real client, 2 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.