CSS - font-size-adjust Property
CSS font-size-adjust property is used to adjust the font size of an element to maintain consistent readability when the font-family is changed. It helps ensure that text appears at a similar size across different fonts, which can be particularly useful when using a fallback font.
Syntax
font-size-adjust: none | number | initial | inherit;
Property Values
| Value | Description |
|---|---|
| none | It specifies that no font size adjustment is made based on the x-height. Default. |
| number | It specifies a numerical value that represents the aspect value, which is the ratio of the x-height of the font to the x-height of the font specified by the font-family property. |
| initial | This sets the property to its initial value. |
| inherit | This inherits the property from the parent element. |
Examples of CSS Font Size Adjust Property
The following examples explain the font-size-adjust property with different values.
Font Size Adjust Property with None Value
To prevent any adjustment based on the aspect ratio of the font, and to use the specified font size directly without modifying it according to the font's x-height, we use the none value for the font-size-adjust property. This is the default value. This is shown in the following example.
Example
<!DOCTYPE html>
<html>
<head>
<style>
body {
font-family: Arial, sans-serif;
font-size: 20px;
}
.adjusted {
font-family: "Georgia", serif;
font-size: 20px;
font-size-adjust: none;
}
</style>
</head>
<body>
<h2>
CSS font-size-adjust property
</h2>
<p>
This is text using the default font family (Arial)
with a font size of 20px.
</p>
<p class="adjusted">
This is text using Georgia with font-size-adjust
set to none. The font size is not adjusted relative
to Georgia's x-height.
</p>
</body>
</html>
Font Size Adjust Property with Numeric Values
To ensure that text maintains consistent readability and size when switching between fonts with different x-heights, we specify a positive value (e.g. 0.25, 1 etc.) to the font-size-adjust property. The value ensures that the text rendered with the next font is consistent in size with the first font. This is shown in the following example.
Example
<!DOCTYPE html>
<html>
<head>
<style>
body {
font-family: Arial, sans-serif;
font-size: 20px;
}
.adjusted {
font-family: "Georgia", serif;
font-size: 20px;
font-size-adjust: 0.5;
}
</style>
</head>
<body>
<h2>
CSS font-size-adjust property
</h2>
<p>
This is text using the default font family.
</p>
<p class="adjusted">
This is text using Georgia with font-size-adjust applied.
</p>
</body>
</html>
Note: Only 'Firefox' browser supports the font-size-adjust property.
Supported Browsers
| Property | ![]() |
![]() |
![]() |
![]() |
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|---|---|---|---|---|---|
| font-size-adjust | Not Supported | Not Supported | 3.0 | Not Supported | Not Supported |




