CSS Properties

letter-spacing

CSS property · 19 supported, 2 partial, 0 unsupported across 21 clients

letter-spacing is safe in 19 of 21 email clients as of Sep 2, 2026, the holdouts are Outlook (New), Outlook Classic.

7/7 webmail, 4/6 desktop, 8/8 mobile clients support letter-spacing fully.
Partial in Outlook (New), Outlook Classic, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support letter-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 Jan 19, 2020, 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 2}
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	Supported
AOL Mail	webmail	AOL	Supported
Fastmail	webmail	Fastmail	Supported
Superhuman	desktop	Blink	Supported

Documented caveats (2)

1.Outlook (New): Partial. Big negative values are rendered differently from CSS standards. Buggy. Values set in em are smaller than the expected render in CSS. See #192.
2.Outlook Classic: Partial. Big negative values are rendered differently from CSS standards.

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

Client-by-client behaviour for letter-spacing

Fully supports letter-spacing (19): Gmail, Gmail Android, Gmail iOS, 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, Proton Mail, AOL Mail, Fastmail, Superhuman.

Partial support (2): Outlook (New), Outlook Classic. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

Fixes & Workarounds

Outlook (New)

Partial

"letter-spacing" is not supported in this email client.

Outlook Classic

Partial

"letter-spacing" is not supported in this email client.

Related Features

!important accent-color align-items animation aspect-ratio backdrop-filter background background-blend-mode

Check your own HTML for letter-spacing

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Test your letter-spacing layout across 21 email clients

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Last tested upstream: Jan 19, 2020 · Last synced by Emailens: Sep 2, 2026

caniemail.com (MIT) records Jan 19, 2020 as the last time letter-spacing was tested in a real client, 6 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.