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Using Custom Web Fonts
Using Custom Web Fonts

Details on custom web fonts supported in the advanced email editor.

Pierce Ujjainwalla avatar
Written by Pierce Ujjainwalla
Updated over a week ago

Apply custom fonts to your emails to add personality and keep your message clear and readable. At the same time, review this article to be aware of how web fonts display in different email clients as not all fonts are fully supported everywhere.

What are web safe fonts?

In most online text editors you tend to find the same, small set of available fonts. Why a small set and why only these fonts? Because they are the ones typically installed on your device. These are the fonts that are normally referred to as "web safe" fonts.

See, the set of fonts available on your computer is defined by the fonts that shipped with your operating system, those added by applications you installed, and individual fonts that you've added manually over time.

As you can imagine, the resulting list of installed fonts can vary greatly from device to device. There is a subset of fonts, however, that are considered a minimum common denominator as they are almost always found. Those are what we refer to as web safe fonts:

  • "safe" because they are available on pretty much every device.

  • "web" because they are used when editing documents online.

In the advanced Knak email editor, you will find these web safe fonts at the top of any font selection tool. They are:

  • Arial

  • Courier

  • Georgia

  • Helvetica

  • Lucida Sans

  • Tahoma

  • Times New Roman

  • Trebuchet MS

  • Verdana

Now, the issue with these fonts is that they are only a handful, and therefore greatly limit design choices in terms of typography. One solution is to expand the set of available fonts by using web fonts.

When can we use web fonts?

Web fonts are available online, served by services like Google fonts. Your device downloads them only when needed (so there is no need for them to be installed in your computer/device). The word "web" in this case refers to "created for the web, and distributed online".

Web fonts are here to help us expand our text style choices and go beyond standard web safe fonts.

Keep in mind that only some email clients support custom fonts. Here is the list of email clients that support web/custom fonts:


  • MacOS Apple Mail

  • Hey for Desktop


  • IOS Mail

  • Samsung Email

  • Proton Mail on Android

  • Orange IOS

Unfortunately Outlook and Gmail on mobile and desktop do not support custom web fonts at this time.

Because of this lack of support, in the Knak advanced email editor we've built font stacks (using cascading style sheets) that automatically tell any email program how to "fall back" to a safe font when that email client is not able to render them. The stacks work as a descendant list of choices: if the first one is not available, it moves to the next. When using a custom font you will see the web safe fallback listed below the font selector:

Font stacks

Fonts are grouped together to offer the best possible fallback solution. This ensures that the layout won't break when the selected font is not supported. The variables we considered when building these font stacks were font shape and font size.

The following is a simplified list of the available font stacks:

Web font › Web safe fallback list of options

Bitter › Georgia › Times › Times New Roman › serif

Droid Serif › Georgia › Times › Times New Roman › serif

Lato › Tahoma › Verdana › Segoe › sans-serif

Open Sans › Helvetica Neue › Helvetica › Arial › sans-serif

Roboto › Tahoma › Verdana › Segoe › sans-serif

Source Sans Pro › Tahoma › Verdana › Segoe › sans-serif

Montserrat › Trebuchet MS › Lucida Grande › Lucida Sans Unicode › Lucida Sans › sans-serif

Ubuntu › Tahoma › Verdana › Segoe › sans-serif

Notice that we've kept an eye on the typography design and didn't add fancier or more complex fonts - such as the Lobster font - that wouldn't have an appropriate fallback font.

Japanese fonts

We included two Japanese fonts in the stacks. Hiragino (ヒラギノ角ゴ Pro W3) is provided with Mac OS, while Meiryo (メイリオ) is distributed with Microsoft's latest versions of Windows.

Both stacks are built to cover the most popular configurations:

ヒラギノ角ゴ Pro W3 › Hiragino Kaku Gothic Pro › Osaka › メイリオ › Meiryo › MS Pゴシック › MS PGothic › sans-serif

メイリオ › Meiryo › MS Pゴシック › MS PGothic › ヒラギノ角ゴ Pro W3 › Hiragino Kaku Gothic Pro › Osaka › sans-serif

Need more help? Contact support via live chat within Knak using the chat bubble in the bottom right corner or email

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