CSS At-Rules

@font-face

CSS at-rule · 7 supported, 1 partial, 13 unsupported across 21 clients

As of Sep 2, 2026, @font-face fails or degrades in 14 of 21 email clients, treat it as progressive enhancement, never structure.

1/7 webmail, 4/6 desktop, 2/8 mobile clients support @font-face fully.
Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 9 more.
Partial in Outlook (New), behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support @font-face, and its replacement changes little here; see the deprecation diff.
Documented before/after fixes on this page cover 21 clients, including Gmail and Gmail Android.
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 Dec 19, 2023, synced by Emailens Sep 2, 2026.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Unsupported^{See caveat 1}
Gmail Android	mobile	Gmail Mobile	Unsupported
Gmail iOS	mobile	Gmail Mobile	Unsupported
Outlook 365	webmail	Outlook Web	Unsupported
Outlook (New)	desktop	Outlook Web	Partial^{See caveat 2}
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Unsupported
Outlook Android	mobile	Outlook Mobile	Unsupported
Outlook for Mac	desktop	WebKit	Supported
Apple Mail	desktop	WebKit	Supported
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Unsupported
Yahoo Mail Android	mobile	Yahoo	Unsupported
Yahoo Mail iOS	mobile	Yahoo	Unsupported
Samsung Mail	mobile	Samsung	Supported^{See caveat 3}
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Supported
Proton Mail	webmail	Proton	Unsupported
AOL Mail	webmail	AOL	Unsupported
Fastmail	webmail	Fastmail	Unsupported
Superhuman	desktop	Blink	Supported

Documented caveats (3)

1.Gmail: Not supported. Roboto and Google Sans can be used, but only because they're embedded with the webmail's own styles.
2.Outlook (New): Partial. The declaration is supported but distant fonts are ignored.
3.Samsung Mail: Not supported when using a Microsoft email address; outlook, live, hotmail, etc.

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

Client-by-client behaviour for @font-face

Fully supports @font-face (7): Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Superhuman.

Partial support (1): Outlook (New). Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (13): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook Classic, Outlook iOS, Outlook Android, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Proton Mail, AOL Mail, Fastmail. Plan fallbacks for these clients before relying on @font-face in production sends.

Fixes & Workarounds

Gmail

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Gmail Android

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Gmail iOS

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Outlook 365

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Outlook Classic

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Outlook iOS

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Outlook Android

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Yahoo Mail

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Yahoo Mail Android

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Yahoo Mail iOS

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Proton Mail

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

AOL Mail

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Fastmail

Unsupported

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Outlook (New)

Partial

Always include a web-safe font stack as fallback (e.g., Arial, Helvetica, sans-serif).

Before (Broken)

before.html

5 lines

@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

After (Fixed)

fixed.html

8 lines

/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}

Add web-safe font fallback stack

Production guidance for @font-face

@font-face is a CSS at-rule. Across the email client matrix, 7 of 21 tracked clients support it fully, 1 only partially, and 13 not at all. The clients most likely to require a workaround for this feature are Gmail, Gmail Android, Gmail iOS. Each of them needs a tailored fallback. See the per-client examples above for the specific code fix Emailens recommends.

When in doubt, ship a baseline that renders without @font-face and treat it as progressive enhancement on clients where support is verified. Emailens automatically detects cross-client divergence on this feature when you preview an email, so you can see exactly which template paths break before a campaign goes out.

Related Features

@import @keyframes @media @media device-pixel-ratio @media hover @media orientation @media prefers-color-scheme @media prefers-reduced-motion

Check your own HTML for @font-face

Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.

Zero-Friction Engine Preview

Test your @font-face layout across 21 email clients

Preview rendering, catch CSS issues, and see how @font-face displays across Outlook, Gmail, and Apple Mail. Free, no account needed.

Instant live preview · No signup required · 21 email engines

Last tested upstream: Dec 19, 2023 · Last synced by Emailens: Sep 2, 2026

caniemail.com (MIT) records Dec 19, 2023 as the last time @font-face was tested in a real client, 2 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.