Firefox 78 Released, Enables CSS :is and :where Selectors

Browser News

Firefox 78 was released on 30th June, 2020. Major web platform updates in this version include :

  • CSS :is() and :where() pseudo-classes are enabled. Both these are useful for writing large selectors in a more concise form.

    /* old way */
    header p,
    main p,
    footer p {
    	color: red;
    /* new way using :is() */
    :is(header, main, footer) p {
    	color: red;

    :is() and :where() differ in specificity.

  • New features have been added to Javascript regular expressions as per ES2018 :
    • Lookbehind assertions — basically a regular expression can read backwards for a match
    • dotAll property — that indicates whether or not "s" flag in used in the regex
    • Unicode property escapes — for allowing character matching based on Unicode
    • Named capture groups — basically names can be specified for returned matches in a group
  • replaceChildren() DOM method has been implemented. Like the name suggests, this replaces existing children of a DOM Node with new set of child nodes.
  • Intl.ListFormat API is supported
  • And more

Read the full Mozilla blog post.

June 30, 2020


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