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text-size-adjust

Experimental: 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: revert;
text-size-adjust: revert-layer;
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.

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 definition

Initial value	`auto` for smartphone browsers supporting inflation, `none` in other cases (and then not modifiable).
Applies to	all elements
Inherited	yes
Percentages	yes, refer to the corresponding size of the text font
Computed value	as specified
Animation type	discrete

Formal syntax

text-size-adjust = 
  auto                |
  none                |
  <percentage [0,∞]>

Examples

Basic disabling usage

As hinted at above, on a properly designed responsive site the text-size-adjust behavior is not needed, so developers can elect to turn it off by specifying a value of none:

p {
  -webkit-text-size-adjust: none;
  text-size-adjust: none;
}

Specifications

Specification
CSS Mobile Text Size Adjustment Module Level 1 # adjustment-control

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`text-size-adjust`	54	7912–79	No	No	41	No	54	54	4914	41	1	6.0
`percentages`	54	12	No	No	41	No	54	54	No	41	No	6.0