The download attribute for <a> elements loads the target URL as a file to be saved, instead of navigating to it. An optional attribute value sets a default file name.

The touch-action CSS property sets whether an element on a touch screen can be panned or pinched to zoom.

The AbortController and AbortSignal APIs allow you to cancel an ongoing operation, such as a fetch() request.

If you construct a fetch request with an AbortSignal, you can cancel the request.

The mediaKeys property of HTMLMediaElement and the navigator.requestMediaKeySystemAccess() method control the playback of content subject to digital rights management. Also known as EME.

The IntersectionObserver API asynchronously observes changes in the intersection of a target element with an ancestor element or with a top-level document's viewport.

In printed page layouts, the break-after, break-before, break-inside CSS properties control where printed pages start and end. Also known as pagination or page breaking.

Methods that validate form controls before submission, such as checkValidity(), reportValidity() and setCustomValidity().

The pointer, any-pointer, hover, and any-hover CSS media queries set styles based on the presence of pointing devices and their ability to hover over elements. For example, most smartphones match the (hover: none) and (pointer: coarse) media query.

The -webkit-device-pixel-ratio, -webkit-min-device-pixel-ratio, and -webkit-max-device-pixel-ratio CSS media queries are standardized compatibility alternatives to resolution media queries.

The <meter> element represents a scalar value within a known range or a fractional value, typically shown as a progress bar.

The <output> element represents the result of a calculation, user action, or form entry.

The promise finally() method executes a function when the promise settles (resolves or rejects).

The overflow-wrap CSS property breaks a line of text onto multiple lines inside the targeted element in an otherwise unbreakable place to prevent overflow. The legacy property is word-wrap.

The tabindex HTML attribute make an element focusable, and sets the element's relative ordering for sequential focus navigation.

The SpeechSynthesis API converts text to speech with artificial voices.

The font-variation-settings CSS property sets an "axis of variability" on a variable font, such as weight, optical size, or a custom axis defined by the typeface designer. When possible, use other CSS font properties, such as font-weight: bold. Also known as variable fonts.

Arrays are iterable with the for … of statement and enumerable with the methods entries(), keys(), and values().

JavaScript modules allow code to be organized into reusable units. Modules use import to load other modules and export to declare what is available to import from other modules. In HTML, modules are loaded with <script type="module">.

The EXT_blend_minmax extension for WebGL 1.0 contexts adds two blend equations, the minimum and maximum color components of the source and destination colors.

The OES_vertex_array_object extension for WebGL 1.0 contexts adds vertex array objects (VAOs) which encapsulate vertex array states. These objects keep pointers to vertex data and names for different sets of vertex data.

The service worker of a website is a script that runs in its own thread and which acts as local proxy that intercepts network requests from the website. Use a service worker to implement advanced caching strategies, offline support, background tasks, or push notification support on your website.

Subresource integrity verifies that a resource, such as script served from a content delivery network, matches a known cryptographic hash. Also known as SRI.

The Upgrade-Insecure-Requests HTTP request header tells the server that the response should redirect to a secure (HTTPS) resource.

The WEBGL_lose_context extension for WebGL 1.0 and 2.0 contexts simulates losing and restoring a WebGLRenderingContext or WebGL2RenderingContext.

The navigator.sendBeacon() method asynchronously sends an HTTP POST request with a limited amount of data, typically for app state, events, and analytics data. The one-way beacon is guaranteed to be initiated before the browser unloads the page, but the sender does not get to handle the response.

The isSecureContext global property is a boolean for whether the current browsing context is secure. This is primarily a check that the page has been served over an HTTPS URL.

The spellcheck global HTML attribute sets whether the browser may check an element for spelling errors.

The <data> element links a given piece of content with a machine-readable translation.

The <time> HTML element represents a time, such as a calendar date, clock time, or duration. It may include the datetime attribute to translate dates into machine-readable format.