The optional alpha parameter of a 2D canvas's getContext() method sets whether the canvas has an alpha transparency channel. If set to false, then this permits the browser to optimize compositing for an opaque canvas.

The ::column CSS pseudo-element represents the individual columns of a multi-column layout container. Columns can only be styled with scroll snap CSS properties and can also have a ::scroll-marker pseudo-element, which scrolls to the column when activated.

The ::marker CSS pseudo-element selects list item markers for styling numbers or bullets.

The ::scroll-button(<dir>) CSS pseudo-element is a focusable button which scrolls its originating scroll container element in the specified direction.

The ::selection CSS pseudo-element selects text a user has highlighted.

The ::spelling-error and ::grammar-error CSS pseudo-elements match text that is highlighted as misspelled and grammatically incorrect, respectively.

The :autofill pseudo-class matches <input> elements that have been filled in automatically by the browser.

The :has-slotted CSS pseudo-class matches <slot> elements where the fallback content is not shown. The pseudo-class matches any slotted content, including white space, text nodes, or elements.

The :host-context() CSS pseudo-class selects the containing element of the shadow tree in which it is used if that element or an ancestor matches the provided selector.

The :target-within CSS pseudo-class matches the element with an ID matching the URL fragment and its ancestors.

The <datalist> element sets recommended values for an <input> element. Browsers may show a dropdown menu of all values or match values as the user types.

The closedby HTML attribute for <dialog> sets which user actions close a dialog. For example, closedby="any" allows the dialog to be closed by clicking outside of it.

The <fencedframe> element embeds another HTML page into the current page in a more secure and privacy-preserving way than <iframe> elements.

The <geolocation> HTML element represents a button that, upon activation, prompts the user to choose whether to grant the page access to geolocation data.

The sizes="auto" attribute for the <img> HTML element sets the layout size for the image based on the computed layout size when choosing a source from the srcset. This attribute only applies to images with the loading="lazy" attribute.

The switch attribute, when present on an <input type="checkbox"> HTML element, renders a switch control with an on and off state instead of a checkbox control.

The <input type="color"> HTML element shows a color picker from which users can choose a color value.

The <install> HTML element represents a button that, upon activation, prompts the user to choose whether to install a progressive web app.

The rel="expect" attribute for the <link> HTML element is a hint to the browser to block rendering until the element that the href value references is connected to the document and fully parsed.

The rel="prefetch" attribute for the <link> HTML element is a hint to the browser that the user is likely to navigate to a resource, so the browser should preemptively fetch and cache the resource.

The name="application-title" attribute for the <meta> HTML element sets an installed web application's title bar text.

The <meta name="text-scale" content="scale" /> HTML element allows the browser's initial font size to be affected by the operating system text scale settings. The <meta name="text-scale" content="legacy" /> element is the default behavior that respects only browser font-size settings.

The name="theme-color" attribute for the <meta> HTML element suggests a color that the browser can use to customize the display of the page or the browser user interface.

The <template for="…"> HTML element replaces the content at a named range or insertion point, marked by the processing instructions <?start name="…"> and <?end> or <?marker name="…">. You can use this to stream or "patch" partial updates into the document out of order.

The <usermedia> HTML element represents a button that, upon activation, toggles camera or microphone streams. If needed, it may prompt the user to choose whether to grant the page access to the camera and microphone.

The @function CSS at-rule defines a custom function that takes CSS values or custom properties as arguments, and returns a CSS value. It can be based on conditional logic such as by using the @media at-rule.

The @mixin and @apply CSS at-rules define reusable style declaration fragments and apply them inside rules, optionally passing arguments.

The Accelerometer, LinearAccelerationSensor and GravitySensor APIs read the acceleration applied to a device in three dimensions, either including the effect of gravity, without its effect, or only its effect, respectively.

The __defineGetter__() and __defineSetter__() methods of objects bind a function to a property, which is called on setting or reading the property.

The Ad Selection API facilitates advertisement sales by allowing sites to register users as part of an interest group or to choose which ads appear based on those interest groups, while minimizing the ability of advertisers to track specific members of the interest group.