CSS Properties

word-spacing

CSS property · 13 supported, 3 partial, 3 unsupported across 21 clients

13 of 21 email clients render word-spacing fully (Sep 2, 2026 data); it breaks outright in Outlook (New), Outlook Classic, AOL Mail.

3/7 webmail, 4/6 desktop, 6/8 mobile clients support word-spacing fully.
Unsupported in Outlook (New), Outlook Classic, AOL Mail.
Partial in Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support word-spacing, 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 13, 2024, 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	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^{See caveat 1}
Yahoo Mail Android	mobile	Yahoo	Partial^{See caveat 1}
Yahoo Mail iOS	mobile	Yahoo	Partial^{See caveat 1}
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Unknown
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Unsupported
Fastmail	webmail	Fastmail	Unknown
Superhuman	desktop	Blink	Supported

Documented caveats (1)

1.Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS: Does not support rem and ch values.

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

Client-by-client behaviour for word-spacing

Fully supports word-spacing (13): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, Proton Mail, Superhuman.

Partial support (3): 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 (3): Outlook (New), Outlook Classic, AOL Mail. Plan fallbacks for these clients before relying on word-spacing in production sends.

Behaviour unverified in: HEY Mail, Fastmail.