HTML 5.1

Changes

This section summarises substantial substantive changes between this specification and [HTML5].

Features added

• The picture and srcset attributes allow responsive image selection.

• The details andsummary elements enable authors to provide extended information that users can choose whether to read.

• The menuitem and type="context" attribute value enable authors to add functionality to the browser’s context menu.

• The requestAnimationFrame API allows for more efficient animation.

• enqueueJob and nextJob help explain Promise resolution in terms of microtasks.

• The rev attribute for links, primarily to support RDFa (previously defined in HTML 4).

• HTMLMediaElement and srcObject objects.

• Enable cross-origin track and EventSource and cross-origin content for ImageBitmap in canvas.

• event-source-error, event-track-error and event-track-load events for media fetching.

• onrejectionhandled and onunhandledrejection and APIs for tracking promise rejection.

• HTMLTableCaptionElement, HTMLTableSectionElement, HTMLTableRowElement, for HTML table elements.

• history.scrollRestoration to control where a users' view is directed when navigating through their history.

• IDL [SameObject], for some objects that return collections.

• Add "noopener" to rel and window to allow for browsing contexts to be separated.

• nonce attribute on script and style to support the use of Content Security Policy.

Features removed

• appCache.

• Media Controllers.

• The command API.

• The usemap attribute on object.

• The accessKeyLabel IDL attribute.

• The form attribute is no longer valid for label.

• The multiple attribute on input type="range".

• hreflang andtype attributes on area.

• The use of nested section elements each with an h1 to create an outline.

• Special handling of isindex in form submission.

• navigator.yieldForStorageUpdates() and the Storage mutex.

• Disallow tfoot before tbody.

• [Exposed=Window] for HTMLHyperLinkElementUtils, [Exposed=Window, Worker] for DOMStringMap and IDL Date.

Changes to existing features

• The accesskey takes a single character as a value (as in HTML 4).

• header and footer elements can be nested, if each level is within a sectioning element.

• option elements can be empty.

• The mousewheel event is called wheel.

• The value attribute of input type="submit" is translatable.

• A figcaption can appear anywhere within a figure.

• Having title, or writing email to a friend does not make an img missing alt conformant.

• The content of time is phrasing content, or text.

• Blank alt on area elements with duplicate href attributes is no longer conformant.

• When navigating internally, the next search for a link etc starts from where the navigation moved to.

• img and related elements support width="0".

• .tFoot and .createTFoot() always insert at the end of a table

• fieldset and namedItem make HTMLCollections not HTMLFormControlsCollections and HTMLOptionsCollections.

• frameElement can return null.

• For images which don’t resolve currentSrc is the URL given to the resolver, not necessarily the absolute URL.

• script IDL attributes reflect.

• meta refresh allows ; or url= to be optional.

• navigator.javaEnabled() is a method.

• fileCallback is called blobcallback.

• The toBlob() callback is non-nullable.

• origin on HTMLHyperlinkElementUtils and Location is readonly.

• The first title child of an SVG is its title, not the last.

• window.open() can return null