This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The text-size-adjust CSS property controls the text inflation algorithm used on some smartphones and tablets. Other browsers will ignore this property.

/* Keyword values */
text-size-adjust: none;
text-size-adjust: auto;

/* <percentage> value */
text-size-adjust: 80%;

/* Global values */
text-size-adjust: inherit;
text-size-adjust: initial;
text-size-adjust: unset;

Because many websites have not been developed with small devices in mind, mobile browsers differ from desktop browsers in the way they render web pages. Instead of laying out pages at the width of the device screen, they lay them out using a viewport that is much wider, usually 800 or 1000 pixels. To map the extra-wide layout back to the original device size, they either show only part of the whole render or scale the viewport down to fit.

Since text that has been scaled down to fit a mobile screen may be very small, many mobile browsers apply a text inflation algorithm to enlarge the text to make it more readable. When an element containing text uses 100% of the screen's width, the algorithm increases its text size, but without modifying the layout. The text-size-adjust property allows web authors to disable or modify this behavior, as web pages designed with small screens in mind do not need it.

Initial valueauto for smartphone browsers supporting inflation, none in other cases (and then not modifiable).
Applies toall elements
Inheritedyes
Percentagesyes, refer to the corresponding size of the text font
Mediavisual
Computed valueas specified
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar

Syntax

The text-size-adjust property is specified as none, auto, or a <percentage>.

Values

none
Disables the browser's inflation algorithm.
auto
Enables the browser's inflation algorithm. This value is used to cancel a none value previously set with CSS.
<percentage>
Enables the browser's inflation algorithm, specifying a percentage value with which to increase the font size.

Formal syntax

none | auto | <percentage>

Specifications

Specification Status Comment
CSS Mobile Text Size Adjustment Module Level 1
The definition of 'text-size-adjust' in that specification.
Editor's Draft Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

54

No -webkit- 1

12 -webkit- No No42

No

No -webkit- 3

<percentage> ? Yes No No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support5454

Yes -ms-

Yes -webkit-

Yes -moz-

49 -webkit-

44 -webkit- 2

42 Yes -webkit- 6.0
<percentage> ? ? Yes No No Yes ?

1. Instead of ignoring the -webkit-text-size-adjust property, a bug prevents desktop Chrome users from zooming in or out. The bug was fixed after Chrome 26.

2. From version 44: this feature is behind the layout.css.prefixes.webkit preference (needs to be set to true). To change preferences in Firefox, visit about:config.

3. Instead of ignoring the -webkit-text-size-adjust property, a bug prevents desktop Safari users from zooming in or out. The bug was fixed after Safari 5.

See also