Time for a review of Firefox 92

Release time comes around so quickly! This month we have quite a few CSS updates, along with the new Object.hasOwn() static method for JavaScript.

This blog post provides merely a set of highlights; for all the details, check out the following:

CSS Updates

A couple of CSS features have moved from behind a preference and are now available by default: accent-color and size-adjust.


The accent-color CSS property sets the color of an element’s accent. Accents appear in elements such as a checkbox or radio input. It’s default value is auto which represents a UA-chosen color, which should match the accent color of the platform. You can also specify a color value. Read more about the accent-color property here.


The size-adjust descriptor for @font-face takes a percentage value which acts as a multiplier for glyph outlines and metrics. Another tool in the CSS box for controlling fonts, it can help to harmonize the designs of various fonts when rendered at the same font size. Check out some examples on the size-adjust descriptor page on MDN.

And more…

Along with both of those, the break-inside property now has support for values avoid-page and avoid-column, the font-size-adjust property accepts two values and if that wasn’t enough system-ui as a generic font family name for the font-family property is now supported.

break-inside property on MDN

font-size-adjust property on MDN

font-family property on MDN

Object.hasOwn arrives

A nice addition to JavaScript is the Object.hasOwn() static method. This returns true if the specified property is a direct property of the object (even if that property’s value is null or undefined). false is returned if the specified property is inherited or not declared. Unlike the in operator, this method does not check for the specified property in the object’s prototype chain.

Object.hasOwn() is recommended over Object.hasOwnProperty() as it works for objects created using Object.create(null) and with objects that have overridden the inherited hasOwnProperty() method.

Read more about Object.hasOwn() on MDN

About Ruth John

Ruth John works as a Technical Writer at Mozilla. A recent addition to the MDN team, she's a big fan of web technologies, and not only enjoys writing about them, but building demos with them as well.

More articles by Ruth John…


  1. John

    Super! thanks!

    September 14th, 2021 at 07:27

  2. Youdon Tneedthat

    accent-color css is pretty cool!

    September 22nd, 2021 at 02:50

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