Mozilla CSS support chart

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This page lists supported CSS selectors, properties, @-rules, Media queries and values in alphabetical order.

The "supported since" column indicates the Gecko version number in which support was introduced; versions prior to Gecko 1.0 are listed as 1.0.

Gecko is the rendering engine used in Firefox and other applications; please see Gecko for more information about Firefox and Gecko version numbers.

The "specification" column links to one of the specifications in which the feature was first specified.  However, in many cases, the feature in also specified, and extended, in newer specifications.  The compatibility list in each specific article gives the detail of the specification history.

Mozilla CSS extensions (those prefixed with -moz-) are mentioned in the "Notes" column to provide bug numbers and other hints regarding CSS support.

Warning: Various specifications are still Working Drafts and several properties can be deleted, changed or renamed.

If you think you have found a bug in Mozilla's CSS support, please create a minimal test case and file a bug. Make sure you search through existing bugs first.

This chart refers to the CSS 2.1 Specification and current drafts by the CSS Workgroup.

Selectors

Selector Initial specification Supported by Gecko Notes
Specification status Since
Basic Selectors
Universal Selector * CSS Level 2 (Revision 1) Yes
Recommendation 1.0
Type selector element CSS Level 1 Yes
Recommendation 1.0
Class selector .class CSS Level 1 Yes
Recommendation 1.0
ID selector #id CSS Level 1 Yes
Recommendation 1.0
Attribute selectors [attribute="value"] CSS Level 2 (Revision 1) Yes
Recommendation 1.0
Combinators
Descendant selector E F CSS Level 1 Yes
Recommendation 1.0
Child selector E > F CSS Level 2 (Revision 1) Yes
Recommendation 1.0
Adjacent sibling selector E + F CSS Level 2 (Revision 1) Yes
Recommendation 1.0
General sibling selectors E ~ F Selectors Level 3 Yes
Recommendation 1.0
Pseudo-elements
:after (::after) CSS 3 (Selectors) Yes Syntax with two colons (::) is supported since Gecko 1.5
Recommendation 1.0 (1.5)
:before (::before) CSS 3 (Selectors) Yes
Recommendation 1.0 (1.5)
:first-letter (::first-letter) CSS 3 (Selectors) Yes
Recommendation 1.0 (1.5)
:first-line (::first-line) CSS 3 (Selectors) Yes
Recommendation 1.0 (1.5)
::selection CSS 3 (Selectors) No ::-moz-selection is supported since Gecko 1.5
Recommendation
Dynamic pseudo-classes
:link CSS 3 (Selectors) Yes -
Recommendation 1.0
:visited CSS 3 (Selectors) Yes -
Recommendation 1.0
:active CSS 3 (Selectors) Yes -
Recommendation 1.0
:hover CSS 3 (Selectors) Yes -
Recommendation 1.0
:focus CSS 3 (Selectors) Yes -
Recommendation 1.0
Structural pseudo-classes
:root CSS 3 (Selectors) Yes -
Recommendation 1.0
:empty CSS 3 (Selectors) Yes Since Gecko 1.8 an element containing spaces does not longer match :empty
Recommendation 1.0
:first-child CSS 3 (Selectors) Yes -
Recommendation 1.0
:last-child CSS 3 (Selectors) Yes -
Recommendation 1.0
:only-child CSS 3 (Selectors) Yes -
Recommendation 1.8
:first-of-type CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:last-of-type CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:only-of-type CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:nth-child CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:nth-last-child CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:nth-of-type CSS 3 (Selectors) Yes -
Recommendation 1.9.1
:nth-last-of-type CSS 3 (Selectors) Yes -
Recommendation 1.9.1
UI pseudo-classes
:enabled CSS 3 (Selectors) Yes -
Recommendation 1.1
:disabled CSS 3 (Selectors) Yes -
Recommendation 1.1
:check CSS 3 (Selectors) Yes -
Recommendation 1.1
:indeterminate CSS 3 (Selectors) Yes -
Recommendation 1.9.2
:default CSS 3 (UI) Yes -
Recommendation 1.9
:valid CSS 3 (UI) Yes -
Recommendation 2.0
:invalid CSS 3 (UI) Yes -
Recommendation 2.0
:in-range CSS 3 (UI) No -
Recommendation 1.0
:out-of-range CSS 3 (UI) No -
Recommendation 1.0
:required CSS 3 (UI) Yes -
Recommendation 1.0
:optional CSS 3 (UI) Yes -
Recommendation 2.0
:read-only CSS 3 (UI) No -
Recommendation 1.0
:read-write CSS 3 (UI) No -
Recommendation 1.0
::value CSS 3 (UI) No -
Recommendation 1.0
::choices CSS 3 (UI) No -
Recommendation 1.0
::repeat-item CSS 3 (UI) No -
Recommendation 1.0
::repeat-index CSS 3 (UI) No -
Recommendation 1.0
Other pseudo-classes
:lang CSS 3 (Selectors) Yes -
Recommendation 1.2
:not CSS 3 (Selectors) Yes -
Recommendation 1.0
:target CSS 3 (Selectors) Yes -
Recommendation 1.3

Properties

Property Specification Supported Supported since Notes
animation CSS 3 (Animations) Yes 16.0 -moz-animation is supported since Gecko 5.0.
animation-delay CSS 3 (Animations) Yes 16.0 -moz-animation-delay is supported since Gecko 5.0.
animation-direction CSS 3 (Animations) Yes 16.0 -moz-animation-direction is supported since Gecko 5.0.
animation-duration CSS 3 (Animations) Yes 16.0 -moz-animation-duration is supported since Gecko 5.0.
animation-fill-mode CSS 3 (Animations) Yes 16.0 -moz-animation-fill-mode is supported since Gecko 5.0.
animation-iteration-count CSS 3 (Animations) Yes 16.0 -moz-animation-iteration-count is supported since Gecko 5.0.
animation-name CSS 3 (Animations) Yes 16.0 -moz-animation-name is supported since Gecko 5.0.
animation-play-state CSS 3 (Animations) Yes 16.0 -moz-animation-play-state is supported since Gecko 5.0.
animation-timing-function CSS 3 (Animations) Yes 16.0 -moz-animation-timing-function is supported since Gecko 5.0.
appearance CSS 3 (UI) No - -moz-appearance is supported since Gecko 1.0.
background CSS 3 (Background) Yes 1.0 (1.9.2) Multiple backgrounds are supported since Gecko 1.9.2.
background-attachment CSS 3 (Background) Yes 1.0 (1.9.2)
background-clip CSS 3 (Background) Yes 2.0 -moz-background-clip was supported since Gecko 1.2 till 1.9.2.
background-color CSS 3 (Background) Yes 1.0 -
background-image CSS 3 (Background) Yes 1.0 (1.9.2) Multiple backgrounds are supported since Gecko 1.9.2.
background-origin CSS 3 (Background) Yes 2.0 -moz-background-origin was supported since Gecko 1.2 till 1.9.2.
background-position CSS 3 (Background) Yes 1.0 (1.9.2) Multiple backgrounds are supported since Gecko 1.9.2.
background-repeat CSS 3 (Background) Yes 1.0 (1.9.2)
background-size CSS 3 (Background) Yes 2.0 -moz-background-size was supported in Gecko 1.9.2.
border CSS 3 (Background) Yes 1.0 -
border-bottom CSS 3 (Background) Yes 1.0 -
border-bottom-color CSS 3 (Background) Yes 1.0 -
border-bottom-left-radius CSS 3 (Background) Yes 2.0 -moz-border-radius-bottomleft is supported since Gecko 1.0.
border-bottom-right-radius CSS 3 (Background) Yes 2.0 -moz-border-radius-bottomright is supported since Gecko 1.0.
border-bottom-style CSS 3 (Background) Yes 1.0 -
border-bottom-width CSS 3 (Background) Yes 1.0 -
border-collapse CSS 2.1 Yes 1.0 -
border-color CSS 3 (Background) Yes 1.0 -
border-image CSS 3 (Background) Yes 15.0 -moz-border-image is supported since Gecko 1.9.1, but differs from current specification. See bug 497995.
border-image-outset CSS 3 (Background) Yes 15.0 -
border-image-repeat CSS 3 (Background) Yes (15.0) The space value is not supported.
border-image-slice CSS 3 (Background) Yes 15.0 -
border-image-source CSS 3 (Background) Yes 15.0 -
border-image-width CSS 3 (Background) Yes 13.0 -
border-left CSS 3 (Background) Yes 1.0 -
border-left-color CSS 3 (Background) Yes 1.0 -
border-left-style CSS 3 (Background) Yes 1.0 -
border-left-width CSS 3 (Background) Yes 1.0 -
border-radius CSS 3 (Background) Yes 2.0 -moz-border-radius is supported since Gecko 1.0.
border-right CSS 3 (Background) Yes 1.0 -
border-right-color CSS 3 (Background) Yes 1.0 -
border-right-style CSS 3 (Background) Yes 1.0 -
border-right-width CSS 3 (Background) Yes 1.0 -
border-spacing CSS 2.1 Yes 1.0 -
border-style CSS 3 (Background) Yes 1.0 -
border-top CSS 3 (Background) Yes 1.0 -
border-top-color CSS 3 (Background) Yes 1.0 -
border-top-left-radius CSS 3 (Background) Yes 2.0 -moz-border-radius-topleft is supported since Gecko 1.0.
border-top-right-radius CSS 3 (Background) Yes 2.0 -moz-border-radius-topright is supported since Gecko 1.0.
border-top-style CSS 3 (Background) Yes 1.0 -
border-top-width CSS 3 (Background) Yes 1.0 -
border-width CSS 3 (Background) Yes 1.0 -
bottom CSS 2.1 Yes 1.0 -
box-align CSS 3 (Flexbox) No - -moz-box-align is supported since Gecko 1.0.
box-decoration-break CSS 3 (Background) No - -
box-direction CSS 3 (Flexbox) No - -moz-box-direction is supported since Gecko 1.0.
box-flex CSS 3 (Flexbox) No - -moz-box-flex is supported since Gecko 1.0.
box-flex-group CSS 3 (Flexbox) No - -moz-box-flex-group is supported since Gecko 1.0.
box-lines CSS 3 (Flexbox) No - -
box-ordinal-group CSS 3 (Flexbox) No - -moz-box-ordinal-group is supported since Gecko 1.0.
box-orient CSS 3 (Flexbox) No - -moz-box-orient is supported since Gecko 1.0.
box-pack CSS 3 (Flexbox) No - -moz-box-pack is supported since Gecko 1.0.
box-shadow CSS 3 (Background) Yes 2.0 -moz-box-shadow is supported since Gecko 1.9.1.
box-sizing CSS 3 (UI) No - -moz-box-sizing is supported since Gecko 1.0.
caption-side CSS 2.1 Yes 1.4 -
clear CSS 2.1 Yes 1.0 -
clip CSS 2.1 Yes 1.0 -
color CSS 3 (Color) Yes 1.0 -
column-count CSS 3 (MultiCol) No - -moz-column-count is supported since Gecko 1.8.
column-fill CSS 3 (MultiCol) No - -moz-column-fill is supported since Gecko 13.0.
column-gap CSS 3 (MultiCol) No - -moz-column-gap is supported since Gecko 1.8.
column-rule CSS 3 (MultiCol) No - -moz-column-rule is supported since Gecko 1.9.1.
column-rule-color CSS 3 (MultiCol) No - -moz-column-rule-color is supported since Gecko 1.9.1.
column-rule-style CSS 3 (MutliCol) No - -moz-column-rule-style is supported since Gecko 1.9.1.
column-rule-width CSS 3 (MultiCol) No - -moz-column-rule-width is supported since Gecko 1.9.1.
column-span CSS 3 (MultiCol) No - See bug 616436.
column-width CSS 3 (MultiCol) No - -moz-column-width is supported since Gecko 1.8.
columns CSS 3 (MultiCol) No - -moz-columns is supported since Gecko 9.0.
content CSS 2.1 Yes 1.0 -
counter-increment CSS 2.1 Yes 1.8 -
counter-reset CSS 2.1 Yes 1.8 -
cursor CSS 2.1 Yes 1.0 -
direction CSS 2.1 Yes 1.0 -
display CSS 2.1 Yes 1.0 -
empty-cells CSS 2.1 Yes 1.0 -
float CSS 2.1 Yes 1.0 -
font CSS 2.1 Yes 1.0 -
font-family CSS 2.1 Yes 1.0 -
font-size CSS 2.1 Yes 1.0 -
font-size-adjust CSS 3 (Fonts) Yes 1.0 (1.9) Prior to Gecko 1.9 this was supported only on windows.
font-stretch CSS 3 (Fonts) Yes 9.0  
font-style CSS 2.1 Yes 1.0 -
font-variant CSS 2.1 Yes 1.0 -
font-weight CSS 2.1 Yes 1.0 -
height CSS 2.1 Yes 1.0 -
left CSS 2.1 Yes 1.0 -
letter-spacing CSS 2.1 Yes 1.0 -
line-height CSS 2.1 Yes 1.0 -
list-style CSS 2.1 Yes 1.0 -
list-style-image CSS 2.1 Yes 1.0 -
list-style-position CSS 2.1 Yes 1.0 -
list-style-type CSS 2.1 Yes 1.0 -
margin CSS 2.1 Yes 1.0 -
margin-bottom CSS 2.1 Yes 1.0 -
margin-left CSS 2.1 Yes 1.0 -
margin-right CSS 2.1 Yes 1.0 -
margin-top CSS 2.1 Yes 1.0 -
max-height CSS 2.1 Yes 1.7 -
max-width CSS 2.1 Yes 1.0 -
min-height CSS 2.1 Yes 1.7 -
opacity CSS 3 (Color) Yes 1.7 -
orphans CSS 2.1 No - See bug 137367.
outline CSS 2.1 Yes 1.8 -
outline-color CSS 2.1 Yes 1.8 -
outline-offset CSS 3 (UI) Yes 1.8 -
outline-style CSS 2.1 Yes 1.8 -
outline-width CSS 2.1 Yes 1.8 -
overflow CSS 2.1 Yes 1.0 -
overflow-x CSS 3 (Box) Yes 1.8 -
overflow-y CSS 3 (Box) Yes 1.8 -
padding CSS 2.1 Yes 1.0 -
padding-bottom CSS 2.1 Yes 1.0 -
padding-left CSS 2.1 Yes 1.0 -
padding-right CSS 2.1 Yes 1.0 -
padding-top CSS 2.1 Yes 1.0 -
page-break-after CSS 2.1 No - See bug 132035.
page-break-before CSS 2.1 No -
page-break-inside CSS 2.1 Yes 19.0
position CSS 2.1 Yes 1.0 -
quotes CSS 2.1 Yes 1.0 -
resize CSS 3 (UI) Yes 2.0 -
right CSS 2.1 Yes 1.0 -
table-layout CSS 2.1 Yes 1.0 -
text-align CSS 2.1 Yes 1.0 -
text-align-last CSS 3 (Text) No - -moz-text-align-last is supported since Gecko 12.0.
text-decoration CSS 2.1 Yes 1.0 -
text-decoration-color CSS 3 (Text) No - -moz-text-decoration-color is supported since Gecko 6.0.
text-decoration-line CSS 3 (Text) No - -moz-text-decoration-line is supported since Gecko 6.0.
text-decoration-skip CSS 3 (Text) No - -
text-decoration-style CSS 3 (Text) No - -moz-text-decoration-style is supported since Gecko 6.0.
text-indent CSS 2.1 Yes 1.0 -
text-shadow CSS 3 (Text) Yes 1.9.1 -
text-transform CSS 2.1 Yes 1.0 -
top CSS 2.1 Yes 1.0 -
transform (2D) CSS 3 (2D Transforms) Yes 16.0 -moz-transform is supported since Gecko 1.9.1.
transform-origin (2D) CSS 3 (2D Transforms) Yes 16.0 -moz-transform-origin is supported since Gecko 1.9.1.
transform (3D) CSS 3 (3D Transforms) Yes 16.0 -moz-transform is supported since Gecko 10.0
transform-origin (3D) CSS 3 (3D Transforms) Yes 16.0 -moz-transform-origin is supported since Gecko 10.0
transform-style CSS 3 (Transforms) Yes 16.0 -moz-transform-style is supported since Gecko 10.0
transition CSS 3 (Transitions) Yes 16.0 -moz-transition is supported since Gecko 2.0.
transition-delay CSS 3 (Transitions) Yes 16.0 -moz-transition-delay is supported since Gecko 2.0.
transition-duration CSS 3 (Transitions) Yes 16.0 -moz-transition-duration is supported since Gecko 2.0.
transition-property CSS 3 (Transitions) Yes 16.0 -moz-transition-property is supported since Gecko 2.0.
transition-timing-function CSS 3 (Transitions) Yes 16.0 -moz-transition-timing-function is supported since Gecko 2.0.
unicode-bidi CSS 2.1 Yes 1.0 -
vertical-align CSS 2.1 Yes 1.0 -
visibility CSS 2.1 Yes 1.3 -
white-space CSS 2.1 Yes 1.0 -
widows CSS 2.1 No - See bug 137367.
width CSS 2.1 Yes 1.0 -
word-break CSS 3 (Text) Yes 15.0 -
word-spacing CSS 2.1 Yes 1.0 -
word-wrap CSS 3 (Text) Yes 1.9.1 -
z-index CSS 2.1 Yes 1.0 -

@-rules

Rule Specification Supported Supported since Notes
@charset CSS 2.1 Yes 1.0 -
@document CSS 3 Yes 6.0 @-moz-document is supported since Gecko 1.8
@font-face CSS 3 (Fonts) Yes 1.9.1 -
@import CSS 2.1 Yes 1.0 -
@keyframes CSS 3 (Animations) Yes 16.0 @-moz-keyframes is supported since Gecko 5.0
@media CSS 3 (Media Queries) Yes 1.0 -
@namespace CSS 3 (Namespace) Yes 1.0 -
@page CSS 2.1 Yes 19.0 -
@supports CSS 3 Yes 22.0 (18.0) In Gecko 18.0 the @supports at-rule is only supported if the user enables it by setting the config value layout.css.supports-rule.enable to true.

Media queries

Property Specification Supported Supported since Notes
aspect-ratio CSS 3 (MediaQueries) Yes 1.9.1 -
color CSS 3 (MediaQueries) Yes 1.9.1 -
color-index CSS 3 (MediaQueries) Yes 1.9.1 -
device-aspect-ratio CSS 3 (MediaQueries) Yes 1.9.1 -
device-height CSS 3 (MediaQueries) Yes 1.9.1 -
device-width CSS 3 (MediaQueries) Yes 1.9.1 -
grid CSS 3 (MediaQueries) No - -
height CSS 3 (MediaQueries) Yes 1.9.1 -
monochrome CSS 3 (MediaQueries) Yes 1.9.1 -
orientation CSS 3 (MediaQueries) Yes 1.9.1 -
resolution CSS 3 (MediaQueries) Yes 1.9.1 -
scan CSS 3 (MediaQueries) No - -
width CSS 3 (MediaQueries) Yes 1.9.1 -

Values and Units

Value / Unit Specification Supported Supported since Notes
Keywords
inherit CSS 3 (Cascade) Yes 1.0 -
initial CSS 3 (Cascade) No - -moz-initial is supported since Gecko 1.9.
Functions
attr() CSS 3 (Values) No 1.0 Only supported for text in content properties. See bug 435426.
calc() CSS 3 (Values) Yes 19.0 -moz-calc is supported since Gecko 2.0 See bug 363249.
counter() CSS 3 (Values) Yes 1.0 -
url() CSS 3 (Values) Yes 1.0 -
Colors
HTML4 color keywords CSS 3 (Color) Yes 1.0 -
SVG color keywords CSS 3 (Color) Yes 1.0 -
System colors CSS 3 (Color) Yes 1.0 -
RGB CSS 3 (Color) Yes 1.0 -
rgba(r,g,b,a) CSS 3 (Color) Yes 1.9 -
hsl(h,s,l) CSS 3 (Color) Yes 1.5 -
hsla(h,s,l,a) CSS 3 (Color) Yes 1.9 -
currentColor CSS 3 (Color) Yes 1.8 -
transparent CSS 3 (Color) Yes 1.9 -
Units
% CSS 3 (Values) Yes 1.0 -
ch CSS 3 (Values) Yes 1.9.1 -
cm CSS 3 (Values) Yes 1.0 -
deg CSS 3 (Values) Yes 1.9.1 -
dpcm CSS 3 (MediaQueries) Yes 1.9.1 -
dpi CSS 3 (MediaQueries) Yes 1.9.1 -
em CSS 3 (Values) Yes 1.0 -
ex CSS 3 (Values) Yes 1.0 -
gd CSS 3 (Values) No - -
grad CSS 3 (Values) Yes 1.9.1 -
Hz CSS 3 (Values) No - -
in CSS 3 (Values) Yes 1.0 -
kHz CSS 3 (Values) No - -
mm CSS 3 (Values) Yes 1.0 -
ms CSS 3 (Values) Yes 2.0 -
pc CSS 3 (Values) Yes 1.0 -
px CSS 3 (Values) Yes 1.0 -
pt CSS 3 (Values) Yes 1.0 -
rad CSS 3 (Values) Yes 1.9.1 -
rem CSS 3 (Values) Yes 1.9.2 -
s CSS 3 (Values) Yes 2.0 -
turn CSS 3 (Values) No - -
vh CSS 3 (Values) Yes 19.0 -
vm CSS 3 (Values) Yes 19.0
vw CSS 3 (Values) Yes 19.0
Images and gradients
image() CSS 3 (Images) No - -
linear-gradient() CSS 3 (Images) Yes 16.0 -moz-linear-gradient() is supported since Gecko 1.9.2.
radial-gradient() CSS 3 (Images) Yes 16.0 -moz-radial-gradient() is supported since Gecko 1.9.2.
repeating-linear-gradient() CSS 3 (Images) Yes 16.0 -moz-repeating-linear-gradient() is supported since Gecko 1.9.2.
repeating-radial-gradient() CSS 3 (Images) Yes 16.0 -moz-repeating-radial-gradient() is supported since Gecko 1.9.2.