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What happens when Aptos fonts aren't available?

The new Aptos range of fonts is only available on Microsoft 365 apps. We investigate what happens when a document, sheet, slide or email with an Aptos font is opened on a computer without Microsoft 365 and the Aptos font range.

In short: if Aptos fonts are not available, it’s not possible to say, for certain, what font will be selected. Most likely it’ll be Calibri or Calibri Light, the previous Office default fonts.

Compare Aptos with Calibri side-by-side and Aptos Display with Calibri Light.

Font selection is more complicated than usual because the Aptos fonts are only available in Microsoft 365 software. Unlike most other fonts which are installed and available to all Windows/Mac programs.

Aptos fonts in Office 2021, Office 2019 and earlier

To see what happens with font substitution, we opened a document with both Aptos (body text) and Aptos Display (headings) in both Word 2021 and Word 2019 using either Windows 11 and Windows 10.

The results were predictable (see below) and also disappointing. Both Aptos and Aptos Display are replaced with the same font, Calibri. Here’s the Font Substitution report from Word 2021/2019.

It’s predictable because, as you’ll see below, both fonts pass the same ‘font family’ information.

Also disappointing because you’d hope that there’d be a different font substitution for Aptos Display, to Calibri Light (the former Heading font default).

Font Substitution 101

Font Substitution is where software chooses a similar font if the font named in the document, email or web page isn’t available.   This often happens when switching between Windows, Mac and portable devices.

Usually, you don’t notice the difference between the original and substituted fonts because common fonts (like those installed with Windows and Mac) have known equivalents.

Font Stacks

A web page, email or document can nominate alternative fonts if the original isn’t available. A ‘font stack’ is common in web pages and emails. 

font-family: Arial, Helvetica, sans-serif;

This HTML/CSS line tells a browser to use Arial font (a Windows default), failing that use Helvetica (a macOS font) and if neither of those is available, a generic sans-serif font.

As we’ll see, only Outlook makes simple use of a font stack. For Word, Excel and PowerPoint you’re at the mercy of whatever Microsoft’s software chooses.


Outlook HTML formatted emails using Aptos or Aptos Display have a very simple font stack. Here’s the CSS used in an email made by Outlook 365 for Windows.

   {font-family:"Aptos Display";}

Both Aptos and Aptos Display fallback to just generic ‘sans-serif’.  We hoped that Microsoft would include ‘Calibri’ fonts as specific alternatives but no. 

That means there’s no direct way to know how an email will appear to a receiver. It’s up to their email software and available fonts to decide what font will be used.

Don’t panic though.  In most cases the substituted font will be a close match, most likely Calibri.

When viewing an Aptos font email in Outlook web with Edge there seems to be a little trickery going on.  The email appears then, after a few moments, switches font. The change is subtle and “blink and you’ll miss it”.

Word, Excel and PowerPoint

Font substitution in Word, Excel and PowerPoint is even more obscure. 

Here’s how the Aptos font is described in the XML code that makes up a Word document.

<w:font w:name="Aptos">
<w:charset w:val="00"/>
<w:family w:val="swiss"/>
<w:pitch w:val="variable"/>
<w:sig w:usb0="20000287" w:usb1="00000003" w:usb2="00000000" w:usb3="00000000" w:csb0="0000019F" w:csb1="00000000"/>

If Aptos font isn’t available, software can use ‘sig’, ‘charset’, ‘pitch’ and ‘family’ details to choose an alternative.  There’s no ‘font stack’ to suggest specific alternatives.

W:family is an obvious clue to help choose an substitute font when the selected font isn’t available. Calibri is also ‘swiss’ font.

Font Embedding

In Office it’s possible to include the required fonts in the document, called Font Embedding. That should ensure that anyone opening the document will see the same fonts. See All about Font Embedding in Microsoft Word

Why and how Windows substitutes Arial font for Helvetica
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