Pseudo-Classes & Selectors

:child-combinator

selector or pseudo-class · 15 supported, 2 partial, 3 unsupported across 21 clients

15 of 21 email clients render :child-combinator 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 :child-combinator 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 :child-combinator, 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 13, 2019, synced by Emailens Sep 2, 2026.

The child combinator (>) selects direct children of a parent. It is supported wherever <style> blocks survive , modern Apple Mail, Superhuman, and conditionally Gmail , and ignored where <style> is stripped. Compared to descendant combinators, the child combinator is more performant and more precise but equally limited in legacy clients.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Supported
Gmail Android	mobile	Gmail Mobile	Partial^{See caveat 1}
Gmail iOS	mobile	Gmail Mobile	Partial^{See 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 :child-combinator

Fully supports :child-combinator (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 :child-combinator in production sends.

Behaviour unverified in: Superhuman.

When to use :child-combinator in email

Styling first-level navigation links without affecting nested submenus.
Targeting top-level cards in a digest layout while leaving inner content untouched.
Constraining responsive overrides to direct children only.

Rendering behaviour and edge cases

Outlook on Windows ignores all selector-based styling because it strips <style> blocks.
Apple Mail and modern Gmail honor the child combinator when <style> survives.
Specificity matters , combine the child combinator with class names rather than tag selectors for predictable cascade order.

Recommended fallback strategy

Use the child combinator inside <style> blocks for clients that honor it, and inline the equivalent styles directly on the matching elements for Outlook compatibility.