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 tab-size CSS property is used to customize the width of a tab (U+0009) character.

Initial value 8
Applies to block containers
Inherited yes
Media visual
Computed value the specified integer or an absolute length
Animation type discrete
Canonical order the unique non-ambiguous order defined by the formal grammar


/* <integer> values */
tab-size: 4;
tab-size: 0;

/* <length> values */
tab-size: 10px;
tab-size: 2em;

/* Global values */
tab-size: inherit;
tab-size: initial;
tab-size: unset;


The number of spaces in a tab. Must be nonnegative.
The width of a tab. Must be nonnegative.

Formal syntax

<integer> | <length>


pre {
  tab-size: 4; /* Set tab size to 4 spaces */
pre {
  tab-size: 0; /* Remove indentation */
pre {
  tab-size: 2; /* Set tab size to 2 spaces */


Specification Status Comment
CSS Text Level 3
The definition of 'tab-size' in that specification.
Working Draft Initial definition

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 21[1] No support 4.0 (2.0)-moz[2] No support 10.60-o
<length> 42 No support 53.0 (53.0)[3] No support No support No support
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mini Opera Mobile Safari Mobile
Basic support 4.4 4.0 (2.0)[2] ? 5-o 11.5-o
<length> ? 53.0 (53.0)[3] ? ? ? ?

[1] The implementation doesn't allow to animate the property yet.

[2] This feature is currently prefixed with -moz. It will be unprefixed in bug 737785. The implementation doesn't allow to animate the property yet. See bug 1308110.

[3] This was implemented in bug 943918.

See also

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