The contain: layout CSS declaration isolates the inside of an element such that it cannot affect the layout of the rest of the page or be affected by the rest of the page. This permits the browser to avoid slower layout calculations.

The contain: paint CSS declaration prevents an element's descendants from being drawn outside the boundaries of the containing element, with any overflow clipped. This permits the browser to avoid slower painting calculations.

The contain: size CSS declaration sets an element's dimensions exclusively by its height and width properties, ignoring its contents and descendants. This permits the browser to avoid slower layout calculations.

The :focus-visible CSS pseudo-class selects elements that match the :focus pseudo-class and meets the browser's criteria for visually emphasizing focused elements.

The navigator.locks API coordinates work with shared resources through mutually exclusive ownership of a resource's name. Also known as web locks.

The transform CSS property and its 3D transform functions allow rotations and other transforms in three dimensions, including perspective transforms.

The <dialog> HTML element represents a modal or non-modal dialog box, such as a confirmation prompt or a subwindow used to enter data.

The appearance CSS property controls the appearance of form controls. Using appearance: none disables any default native appearance and allows the elements to be styled with CSS.

The at() method of arrays and typed arrays returns the item at an index, including negative indices for getting items relative to the end of an array. Also known as the relative indexing method.

The BroadcastChannel API allows you to send messages between same-origin browsing contexts, such as between the same page loaded in multiple tabs.

The @layer CSS at-rule avoids specificity conflicts by providing priority levels for different groups of CSS rules, such as low-priority styles like resets, and high-priority styles like UI components.

The structuredClone() global method creates a deep copy of an object. Values that cannot be cloned can instead be transferred, making the original value no longer usable.

The text-emphasis CSS property sets position and style for text emphasis marks, especially for East Asian languages.

The color-scheme CSS property sets which color schemes (light or dark) an element uses and may prevent automatic dark mode adjustments by the browser.

The font-synthesis CSS shorthand property disables all font synthesis except the given kinds. To disable a specific kind of font synthesis, instead use the longhand properties such as font-synthesis-style and font-synthesis-weight.