The precommitHandler callback option to NavigateEvent's intercept() method returns a promise that defers navigation until the promise resolves. You can use this to change the navigation's URL, state, and history before navigation occurs.

The confidence property of a navigation performance entry describes whether the navigation metric is likely to be representative the page's performance (high confidence) or affected by transient conditions, such as browser startup (low confidence).

The navigator.connection API provides information about the network connection a device is using and fires events when the connection type changes.

Non-cookie storage access extends the requestStorageAccess() API to let content in cross-site iframes request access to first-party data beyond cookies.

The Notification() constructor shows a message to the user, typically using the notification system of the host operating system.

The numeric factory functions, such as CSS.px() or CSS.kHz(), return a CSSUnitValue representing a CSS number value (as in 12px or 440kHz).

The OVR_multiview2 extension for WebGL 2.0 contexts renders into multiple views simultaneously. This especially useful for virtual reality (VR) and WebXR.

The when() method on a event target returns an Observable object, which provides a declarative API for subscribing to and operating on events. It's an alternative to addEventListener() callbacks.

The createValueRange() for form elements, such as <textarea> or <input type="text">, gets an OpaqueRange object that represents a live span of text. You can use this for range-based operations on the input text, such as setting custom highlights or placing autocomplete popovers.

The AbsoluteOrientationSensor and RelativeOrientationSensor APIs describe the physical orientation of a device in three-dimensional space, either in relation to the Earth's coordinate system or in relation to the device's own orientation, respectively.

An Origin object represents an origin, as in a scheme, hostname, and port. You can use it to make same-site and same-origin comparisons.

The page-break-before, page-break-inside, and page-break-after CSS properties are aliases to the break-before, break-inside, and break-after properties.

The page lifecycle API helps you safely handle page suspensions or discards from memory. The freeze and resume events fire when the browser suspends or resumes a page from memory while the document.wasDiscarded property reports whether the page was reloaded after being dropped.

The :first, :left, and :right pseudo-classes select pages based on their position in sequence after pagination.

A visibility-state performance entry measures the timing of page visibility state changes, such as when a tab is no longer visible or the user has switched to another app.

Partitioned cookies allow you to opt a cookie into partitioned storage, with a separate cookie jar per top-level site. Also known as Cookies Having Independent Partitioned State or CHIPS.

The PasswordCredential API represents a username and password.

The payment handler API registers a web application as a payment handler and responds to payment requests in the browser's user interface, rather than redirecting users to a separate site to complete a payment.

The PaymentRequest API prompts the user to make a payment through the browser's user interface.

The window.performance.timing and window.performance.navigation APIs report performance timing information for events that occur during the loading and use of the current page.

The periodic background synchronization API fires a recurring periodicsync event in a service worker. You can use this to update data in the background at regular intervals.

The Permissions-Policy response header and the allow attribute for <iframe> elements sets whether a policy-controlled feature, such as an API, may be used in a document.

Permissions policy violation reporting sends a report to a URL nominated by the Reporting-Endpoints header or the ReportingObserver API when a page violates a policy. You can also use the Permissions-Policy-Report-Only header to receive reports of what might break under a given policy.

The picture-in-picture API allow websites to create a floating, always-on-top video window. Also known as PiP or pop-out video.

Provides access to raw mouse movement by locking the target of mouse events to a single element and hiding the mouse cursor.

The <portal> HTML element embeds another page into the current page as a non-interactive preview.

The Presentation API shows or controls content on another display, such as a network-connected TV or projector.

The attributionsourceid and attributiondestination attributes for <a> elements measure clicks across websites without associating a click to a specific session. Not to be confused with attribution reporting. Also known as PCM.

The Access-Control-Request-Private-Network: true and Access-Control-Allow-Private-Network: true HTTP request and response headers establish permission for websites to make requests to internal networks, such as to routers.

The Profiler API records data about the execution of a page, which you can send to a server for later analysis. Also known as self-profiling.