Pseudo-Classes & Selectors

:checked

selector or pseudo-class · 10 supported, 4 partial, 6 unsupported across 21 clients

10 of 21 email clients render :checked fully (Oct 14, 2026 data); it breaks outright in Gmail, Gmail Android, Gmail iOS and 3 more.

3/7 webmail, 3/6 desktop, 4/8 mobile clients support :checked fully.
Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook Classic and 2 more.
Partial in Outlook 365, Outlook (New), Outlook iOS, Outlook Android, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support :checked, 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 10, 2020, synced by Emailens Oct 14, 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	Partial^{See caveat 1}
Outlook (New)	desktop	Outlook Web	Partial^{See caveat 1}
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Partial^{See caveat 1}
Outlook Android	mobile	Outlook Mobile	Partial^{See caveat 1}
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	Unsupported
Proton Mail	webmail	Proton	Unsupported
AOL Mail	webmail	AOL	Supported
Fastmail	webmail	Fastmail	Supported
Superhuman	desktop	Blink	Unknown

Documented caveats (1)

1.Outlook 365, Outlook (New), Outlook iOS, Outlook Android: Partial. Only supported on type selectors.

Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.

Client-by-client behaviour for :checked

Fully supports :checked (10): Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, AOL Mail, Fastmail.

Partial support (4): Outlook 365, Outlook (New), Outlook iOS, Outlook Android. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (6): Gmail, Gmail Android, Gmail iOS, Outlook Classic, HEY Mail, Proton Mail. Plan fallbacks for these clients before relying on :checked in production sends.

Behaviour unverified in: Superhuman.