This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The text-size-adjust property allows control over the text inflation algorithm used on some mobile devices. As this property is non-standard, it must be prefixed: -moz-text-size-adjust, -webkit-text-size-adjust, and -ms-text-size-adjust.
/* Text is never inflated */ text-size-adjust: none; /* Text may be inflated */ text-size-adjust: auto; /* Text may be inflated in this exact proportion */ text-size-adjust: 80%; /* Global values */ text-size-adjust: inherit; text-size-adjust: initial; text-size-adjust: unset;
Because many web pages have not been developed with mobile in mind, smartphone browsers differ from desktop browsers in the way they display web pages. Instead of laying out the web page at the width of the device screen, they lay it out using a viewport that is much wider than the device screen, usually 800 or 1000 pixels wide. To map the wide layout back to the original device size, the browser either shows only part of the whole render, or the viewport is scaled down to fit.
Because text that has been scaled down to fit a small screen is very small, many mobile browsers apply a text inflation algorithm to make the text larger and more readable. When an element containing text uses 100% of the screen's width, its text size is increased until it reached a readable size, but without modifying the layout.
The text-size-adjust property allows web authors to opt out or modify this behavior, as web pages designed to handle small screen widths do not need it.
- This property is non-standard. You must prefix the property name for each engine you wish to use it on.
- This property's behavior and syntax varies from browser to browser. See the browser compatibility section below for more information.
- This property only works on smartphones and some tablets. Desktop browsers and some tablet browsers have no inflation algorithm.
- If
-webkit-text-size-adjustis explicitly set tonone, older WebKit-based desktop and tablet browsers, like Chrome≤26 or Safari≤5, instead of ignoring the property, will prevent the user from zooming in or out on the web page.# - Not all engines that support this property allow the use of a percentage value (e.g. Webkit and Trident do, but Gecko doesn't). Check the browser compatibility section below for details.
| 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 |
| Media | visual |
| Computed value | as specified |
| Animation type | discrete |
| Canonical order | the 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. On old WebKit-based desktop browsers (Chrome≤26, Safari≤5), this will instead prevent the user from zooming the webpage in or out.
auto- Enables the browser's inflation algorithm. This value is used to cancel a
nonevalue 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
| Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|---|
| Basic support | 54.0[1] | (Yes)-ms (Yes)-webkit |
No support | No support | 42 | No support[1] |
| Percentages | ? | (Yes) -ms | No support | No support | No support | No support |
| Feature | Android | Android Webview | Edge | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|---|
| Basic support | ? | 54.0[1] | (Yes)-ms (Yes)-webkit |
11.0 (11.0) -moz[2] | (Yes) -ms[3] 11-webkit |
42 | (Yes)-webkit | 54.0[1] |
| Percentages | ? | ? | (Yes) -ms | No support | (Yes)[3] | No support | (Yes) | ? |
[1] There is a bug in older WebKit-based desktop browsers. If -webkit-text-size-adjust is explicitly set to none, older Webkit-based desktop browsers, instead of ignoring the property, will prevent the user from zooming in or out of the web page. See Bug 56543 (affected Safari≤5 & Chrome≤26), Bug 163359, and Bug 84186.
[2] In addition to the -moz- prefixed support, Gecko 44.0 (Firefox 44.0 / Thunderbird 44.0 / SeaMonkey 2.41) added support for a -webkit- prefixed version of the property for web compatibility reasons behind the layout.css.prefixes.webkit flag, defaulting to false. Since Gecko 49.0 (Firefox 49.0 / Thunderbird 49.0 / SeaMonkey 2.46) the preference defaults to true.
[3] If the viewport is set using <meta> element, the value of the CSS text-size-adjust property is ignored. See detailed implementation hints on MSDN.
See also
- Apple's documentation.
- Gecko's behavior description by L. David Baron.
- Microsoft's documentation.