CSS Properties

font-size-adjust

CSS property · 9 supported, 5 partial, 2 unsupported across 21 clients

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Supported
Gmail Android	mobile	Gmail Mobile	Partial
Gmail iOS	mobile	Gmail Mobile	Partial
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	Partial
Yahoo Mail Android	mobile	Yahoo	Partial
Yahoo Mail iOS	mobile	Yahoo	Partial
Samsung Mail	mobile	Samsung	Unknown
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Unknown
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Unknown
Fastmail	webmail	Fastmail	Unknown
Superhuman	desktop	Blink	Unknown

Client-by-client behaviour for font-size-adjust

Fully supports font-size-adjust (9): Gmail, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Thunderbird, Proton Mail.

Partial support (5): Gmail Android, Gmail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail 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 (2): Outlook (New), Outlook Classic. Plan fallbacks for these clients before relying on font-size-adjust in production sends.

Behaviour unverified in: Samsung Mail, HEY Mail, AOL Mail, Fastmail, Superhuman.