CSS At-Rules

@font-face

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

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Unsupported
Gmail Android	mobile	Gmail Mobile	Unsupported
Gmail iOS	mobile	Gmail Mobile	Unsupported
Outlook 365	webmail	Outlook Web	Unsupported
Outlook (New)	desktop	Outlook Web	Partial
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
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

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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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

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

After

/* 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 15 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 @supports

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Support data last updated Apr 27, 2026 · synced from caniemail.com via @emailens/engine.