The CSSStyleDeclaration.setProperty() method interface sets a new value for a property on a CSS style declaration object.


style.setProperty(propertyName, value, priority);


  • propertyName is a DOMString representing the CSS property name (hyphen case) to be modified.
  • value Optional is a DOMString containing the new property value. If not specified, treated as the empty string.
    • Note: value must not contain "!important" -- that should be set using the priority parameter.
  • priority Optional is a DOMString allowing the "important" CSS priority to be set. If not specified, treated as the empty string. The following values are accepted:
    • String value "important"
    • Keyword undefined
    • String empty value ""

Return value


  • DOMException (NoModificationAllowedError): if the property or declaration block is read only.

If priority can be omitted, JavaScript has a special simpler syntax for setting a CSS property on a style declaration object:

style.cssPropertyName = 'value';


The following JavaScript code sets a new value for the border-width CSS property on a selector rule:

var declaration = document.styleSheets[0].rules[0].style;
declaration.setProperty('border-width', '1px 2px');
// Equivalent to:
// declaration.borderWidth = '1px 2px';


Specification Status Comment
CSS Object Model (CSSOM)
The definition of 'CSSStyleDeclaration.setProperty()' in that specification.
Working Draft
Document Object Model (DOM) Level 2 Style Specification
The definition of 'CSSStyleDeclaration' in that specification.

Browser compatibility

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ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
setPropertyChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support YesOpera Full support YesSafari Full support 6WebView Android Full support 4.4Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?


Full support  
Full support
Compatibility unknown  
Compatibility unknown