:general-sibling
selector or pseudo-class · 15 supported, 2 partial, 3 unsupported across 21 clients
15 of 21 email clients render :general-sibling fully (Sep 2, 2026 data); it breaks outright in Outlook (New), Outlook Classic, Proton Mail.
- 6/7 webmail, 3/6 desktop, 6/8 mobile clients support :general-sibling fully.
- Unsupported in Outlook (New), Outlook Classic, Proton Mail.
- Partial in Gmail Android, Gmail iOS, behavior differs from browsers, test before relying on it.
- Outlook Classic (Word engine, supported to at least 2029) does not fully support :general-sibling, 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 Mar 11, 2020, synced by Emailens Sep 2, 2026.
Client Support
| Client | Category | Engine | Support |
|---|---|---|---|
| Gmail | webmail | Gmail Web | Supported |
| Gmail Android | mobile | Gmail Mobile | PartialSee caveat 1 |
| Gmail iOS | mobile | Gmail Mobile | PartialSee caveat 1 |
| 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 | Supported |
| 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 | Unsupported |
| AOL Mail | webmail | AOL | Supported |
| Fastmail | webmail | Fastmail | Supported |
| Superhuman | desktop | Blink | Unknown |
Documented caveats (1)
- 1.Gmail Android, Gmail iOS: Partial. Not supported with non Google accounts.
Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.
Client-by-client behaviour for :general-sibling
Fully supports :general-sibling (15): Gmail, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, AOL Mail, Fastmail.
Partial support (2): Gmail Android, Gmail 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, Proton Mail. Plan fallbacks for these clients before relying on :general-sibling in production sends.
Behaviour unverified in: Superhuman.
Fixes & Workarounds
Outlook (New)
Unsupported":general-sibling" is not supported in this email client.
Outlook Classic
Unsupported":general-sibling" is not supported in this email client.
Proton Mail
Unsupported":general-sibling" is not supported in this email client.
Gmail Android
Partial":general-sibling" is not supported in this email client.
Gmail iOS
Partial":general-sibling" is not supported in this email client.
Related Features
Check your own HTML for :general-sibling
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Test your :general-sibling layout across 21 email clients
Preview rendering, catch CSS issues, and see how :general-sibling 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 Mar 11, 2020 as the last time :general-sibling was tested in a real client, 6 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.