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

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 54
Full support 54
No support No
Prefixed Notes
Prefixed Requires the vendor prefix: -webkit-
Notes 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.
Edge Full support 12
Prefixed
Full support 12
Prefixed
Prefixed Requires the vendor prefix: -webkit-
Firefox No support NoIE No support NoOpera Full support 42Safari No support No
No support No
No support No
Prefixed Notes
Prefixed Requires the vendor prefix: -webkit-
Notes 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.
WebView Android Full support 54Chrome Android Full support 54Edge Mobile Full support Yes
Prefixed
Full support Yes
Prefixed
Prefixed Requires the vendor prefix: -ms-
Full support Yes
Prefixed
Prefixed Requires the vendor prefix: -webkit-
Firefox Android Full support Yes
Prefixed
Full support Yes
Prefixed
Prefixed Requires the vendor prefix: -moz-
Full support 49
Prefixed
Prefixed Requires the vendor prefix: -webkit-
Full support 44
Prefixed Disabled
Prefixed Requires the vendor prefix: -webkit-
Disabled 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.
Opera Android Full support 42Safari iOS Full support Yes
Prefixed
Full support Yes
Prefixed
Prefixed Requires the vendor prefix: -webkit-
Samsung Internet Android Full support 6.0
<percentage>
Experimental
Chrome ? Edge Full support YesFirefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android ? Chrome Android ? Edge Mobile Full support YesFirefox Android No support NoOpera Android No support NoSafari iOS Full support YesSamsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.
Requires a vendor prefix or different name for use.
Requires a vendor prefix or different name for use.

See also