CSS Properties

background

CSS property · 15 supported, 6 partial, 0 unsupported across 21 clients

background splits the field: 15 full, 6 partial of 21 clients as of Sep 2, 2026, the partials (Outlook (New), Outlook Classic, Yahoo Mail) are where sends go wrong.

5/7 webmail, 4/6 desktop, 6/8 mobile clients support background fully.
Partial in Outlook (New), Outlook Classic, Yahoo Mail, Yahoo Mail Android and 2 more, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support background, 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 Jul 24, 2023, synced by Emailens Sep 2, 2026.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Supported
Gmail Android	mobile	Gmail Mobile	Supported
Gmail iOS	mobile	Gmail Mobile	Supported
Outlook 365	webmail	Outlook Web	Supported
Outlook (New)	desktop	Outlook Web	Partial^{See caveat 1}
Outlook Classic	desktop	Microsoft Word	Partial^{See caveat 1}
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	Partial^{See caveat 2}
Yahoo Mail Android	mobile	Yahoo	Partial^{See caveat 2}
Yahoo Mail iOS	mobile	Yahoo	Partial^{See caveat 2}
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Supported
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Partial^{See caveat 2}
Fastmail	webmail	Fastmail	Supported
Superhuman	desktop	Blink	Supported

Documented caveats (2)

1.Outlook (New), Outlook Classic: Partial. Only background-color values are supported.
2.Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Partial. Does not support multiple values. The comma between two values is removed. Partial. Does not support the / value shorthand for background-size. But it can be used in the background-size property instead.

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

Client-by-client behaviour for background

Fully supports background (15): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Fastmail, Superhuman.

Partial support (6): Outlook (New), Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.