::marker
pseudo-element · 11 supported, 0 partial, 9 unsupported across 21 clients
11 of 21 email clients render ::marker fully (Sep 2, 2026 data); it breaks outright in Gmail, Gmail Android, Gmail iOS and 6 more.
- 4/7 webmail, 3/6 desktop, 4/8 mobile clients support ::marker fully.
- Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 5 more.
- Outlook Classic (Word engine, supported to at least 2029) does not fully support ::marker, 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 Dec 28, 2022, synced by Emailens Sep 2, 2026.
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 | Unsupported |
| Outlook (New) | desktop | Outlook Web | UnsupportedSee caveat 1 |
| Outlook Classic | desktop | Microsoft Word | Unsupported |
| Outlook iOS | mobile | Outlook Mobile | Unsupported |
| Outlook Android | mobile | Outlook Mobile | Unsupported |
| 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.Outlook (New): Not supported. But
@listdeclarations can achieve the same thing.
Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.
Client-by-client behaviour for ::marker
Fully supports ::marker (11): Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, AOL Mail, Fastmail.
No support (9): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Proton Mail. Plan fallbacks for these clients before relying on ::marker in production sends.
Behaviour unverified in: Superhuman.
Fixes & Workarounds
Gmail
Unsupported"::marker" is not supported in this email client.
Gmail Android
Unsupported"::marker" is not supported in this email client.
Gmail iOS
Unsupported"::marker" is not supported in this email client.
Outlook 365
Unsupported"::marker" is not supported in this email client.
Outlook (New)
Unsupported"::marker" is not supported in this email client.
Outlook Classic
Unsupported"::marker" is not supported in this email client.
Outlook iOS
Unsupported"::marker" is not supported in this email client.
Outlook Android
Unsupported"::marker" is not supported in this email client.
Proton Mail
Unsupported"::marker" is not supported in this email client.
Related Features
Check your own HTML for ::marker
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your ::marker layout across 21 email clients
Preview rendering, catch CSS issues, and see how ::marker 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 Dec 28, 2022 as the last time ::marker was tested in a real client, 3 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.