::before
pseudo-element · 6 supported, 3 partial, 11 unsupported across 21 clients
Client Support
| Client | Category | Engine | Support |
|---|---|---|---|
| Gmail | webmail | Gmail Web | Unsupported |
| Gmail Android | mobile | Gmail Mobile | Unsupported |
| Gmail iOS | mobile | Gmail Mobile | Unsupported |
| Outlook 365 | webmail | Outlook Web | Partial |
| Outlook (New) | desktop | Outlook Web | Unsupported |
| Outlook Classic | desktop | Microsoft Word | Unsupported |
| Outlook iOS | mobile | Outlook Mobile | Partial |
| Outlook Android | mobile | Outlook Mobile | Unsupported |
| Outlook for Mac | desktop | WebKit | Partial |
| Apple Mail | desktop | WebKit | Supported |
| Apple Mail iOS | mobile | WebKit | Supported |
| Yahoo Mail | webmail | Yahoo | Unsupported |
| Yahoo Mail Android | mobile | Yahoo | Unsupported |
| Yahoo Mail iOS | mobile | Yahoo | Unsupported |
| Samsung Mail | mobile | Samsung | Supported |
| Thunderbird | desktop | Gecko | Supported |
| HEY Mail | webmail | WebKit | Supported |
| Proton Mail | webmail | Proton | Unsupported |
| AOL Mail | webmail | AOL | Unsupported |
| Fastmail | webmail | Fastmail | Supported |
| Superhuman | desktop | Blink | Unknown |
Client-by-client behaviour for ::before
Fully supports ::before (6): Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Fastmail.
Partial support (3): Outlook 365, Outlook iOS, Outlook for Mac. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.
No support (11): Gmail, Gmail Android, Gmail iOS, Outlook (New), Outlook Classic, Outlook Android, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Proton Mail, AOL Mail. Plan fallbacks for these clients before relying on ::before in production sends.
Behaviour unverified in: Superhuman.
Fixes & Workarounds
Gmail
Unsupported"::before" is not supported in this email client.
Gmail Android
Unsupported"::before" is not supported in this email client.
Gmail iOS
Unsupported"::before" is not supported in this email client.
Outlook (New)
Unsupported"::before" is not supported in this email client.
Outlook Classic
Unsupported"::before" is not supported in this email client.
Outlook Android
Unsupported"::before" is not supported in this email client.
Yahoo Mail
Unsupported"::before" is not supported in this email client.
Yahoo Mail Android
Unsupported"::before" is not supported in this email client.
Yahoo Mail iOS
Unsupported"::before" is not supported in this email client.
Proton Mail
Unsupported"::before" is not supported in this email client.
AOL Mail
Unsupported"::before" is not supported in this email client.
Outlook 365
Partial"::before" is not supported in this email client.
Outlook iOS
Partial"::before" is not supported in this email client.
Outlook for Mac
Partial"::before" is not supported in this email client.
Related Features
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Try Emailens FreeSupport data last updated Apr 27, 2026 · synced from caniemail.com via @emailens/engine.