🦖 WorkletSharedStorage: entries() method 🦖 https://developer.mozilla.org/en-US/docs/Web/API/WorkletSharedStorage/entries The entries() method of the WorkletSharedStorage interface returns an async iterator. The iterator provides an array of [key, value] pairs corresponding to the enumerable […]

🦖 XSLTProcessor: getParameter() method ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/XSLTProcessor/getParameter The getParameter() method of the XSLTProcessor interface returns the value of a parameter (<xsl:param>) from the stylesheet imported in the […]

🦖 SharedStorageWorkletGlobalScope: register() method 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/SharedStorageWorkletGlobalScope/register The register() method of the SharedStorageWorkletGlobalScope interface registers an operation defined inside the current worklet […]

🦖 DOMRectReadOnly: width property ✅ Widely available (from Jan 2020) https://developer.mozilla.org/en-US/docs/Web/API/DOMRectReadOnly/width The width read-only property of the DOMRectReadOnly interface represents the width of the DOMRect. #webdev

🦖 SVGFEDropShadowElement: height property ✅ Widely available (from Jan 2020) https://developer.mozilla.org/en-US/docs/Web/API/SVGFEDropShadowElement/height The height read-only property of the SVGFEDropShadowElement interface describes the vertical size of an SVG filter primitive as a […]

🦖 DocumentType: after() method ✅ Widely available (from Apr 2018) https://developer.mozilla.org/en-US/docs/Web/API/DocumentType/after The DocumentType.after() method inserts a set of Node objects or strings in the children list of the DocumentType's parent, just after the DocumentType. Strings […]

🦖 Introduction to CSS masking 🦖 https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Masking/Introduction CSS masking enables you to reveal or hide parts of an element selectively by applying one or more mask images to it. These mask images can be gradients, images, or SVG sources. Unlike […]

🦖 Window: outerHeight property ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/Window/outerHeight The Window.outerHeight read-only property returns the height in pixels of the whole browser window, including any sidebar, window chrome, and window-resizing […]

🦖 Intl.PluralRules() constructor ✅ Widely available (from Sept 2019) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/PluralRules/PluralRules The Intl.PluralRules() constructor creates Intl.PluralRules objects. #webdev #javascript

🦖 Intl.Segmenter.prototype.resolvedOptions() ☑️ Newly available (from Apr 2024) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Segmenter/resolvedOptions The resolvedOptions() method of Intl.Segmenter instances returns a new object with properties […]

🦖 DOMRectReadOnly: right property ✅ Widely available (from Jan 2020) https://developer.mozilla.org/en-US/docs/Web/API/DOMRectReadOnly/right The right read-only property of the DOMRectReadOnly interface returns the right coordinate value of the DOMRect. (Has the same value as x + width, or x if […]

🦖 Clients: claim() method ✅ Widely available (from Apr 2018) https://developer.mozilla.org/en-US/docs/Web/API/Clients/claim The claim() method of the Clients interface allows an active service worker to set itself as the controller for all clients within its scope. This triggers a […]

🦖 Accelerometer: Accelerometer() constructor 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/Accelerometer/Accelerometer The Accelerometer() constructor creates a new Accelerometer object which returns the acceleration of the device along all three axes at the time it […]

🦖 URL Pattern API ☑️ Newly available (from Sept 2025) https://developer.mozilla.org/en-US/docs/Web/API/URL_Pattern_API The URL Pattern API defines a syntax that is used to create URL pattern matchers. These patterns can be matched against URLs or individual URL components. #webdev

🦖 :last-child ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Selectors/:last-child The :last-child CSS pseudo-class represents the last element among a group of sibling elements. #webdev #css

🦖 FetchEvent: handled property ✅ Widely available (from Sept 2022) https://developer.mozilla.org/en-US/docs/Web/API/FetchEvent/handled The handled property of the FetchEvent interface returns a promise indicating if the event has been handled by the fetch algorithm or not. This property allows […]

🦖 HTMLTimeElement ✅ Widely available (from Oct 2017) https://developer.mozilla.org/en-US/docs/Web/API/HTMLTimeElement The HTMLTimeElement interface provides special properties (beyond the regular HTMLElement interface it also has available to it by inheritance) for manipulating <time> elements […]

🦖 Report: type property 🦖 https://developer.mozilla.org/en-US/docs/Web/API/Report/type The type read-only property of the Report interface returns the type of report generated, e.g., deprecation or intervention. #webdev

🦖 constructor ✅ Widely available (from Mar 2016) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/constructor The constructor method is a special method of a class for creating and initializing an object instance of that class. #webdev #javascript

🦖 Permissions-Policy: identity-credentials-get directive 🦖 https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/identity-credentials-get The HTTP Permissions-Policy header identity-credentials-get directive controls whether the current document is allowed to […]

🦖 Date.prototype.valueOf() ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/valueOf The valueOf() method of Date instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight […]

🦖 History ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/History The History interface of the History API allows manipulation of the browser session history, that is the pages visited in the tab or frame that the current page is loaded in. #webdev

🦖 Temporal.PlainDate.prototype.equals() 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal/PlainDate/equals The equals() method of Temporal.PlainDate instances returns true if this date is equivalent in value to another date (in a […]

🦖 CSS multi-column layout 🦖 https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Multicol_layout The CSS multi-column layout module lets you divide content across multiple columns. By using the properties in this module, you can define the preferred number and width of columns, the gap size […]

🦖 TextTrack: activeCues property ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/TextTrack/activeCues The activeCues read-only property of the TextTrack interface returns a TextTrackCueList object listing the currently active cues. #webdev

🦖 CSSMathNegate: CSSMathNegate() constructor 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/CSSMathNegate/CSSMathNegate The CSSMathNegate() constructor creates a new CSSMathNegate object which negates the value passed into it. #webdev

🦖 Alt-Used header 🦖 https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Alt-Used The HTTP Alt-Used request header is used to identify the alternative service in use, just as the Host HTTP header field identifies the host and port of the origin. #webdev #http

🦖 HTML elements reference 🦖 https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements This page lists all the HTML elements, which are created using tags. #webdev #html

🦖 CookieStore: change event ☑️ Newly available (from Jun 2025) https://developer.mozilla.org/en-US/docs/Web/API/CookieStore/change_event A change event is fired at a CookieStore object when a change is made to any cookie. #webdev

🦖 :playing 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Selectors/:playing The :playing CSS pseudo-class selector represents the playback state of an element that is playable, such as <audio> or <video>, when that element is "playing". An element is […]

🦖 CSSStyleRule: styleMap property 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleRule/styleMap The styleMap read-only property of the CSSStyleRule interface returns a StylePropertyMap object which provides access to the rule's property-value pairs. #webdev

🦖 MIDIPort: statechange event 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/MIDIPort/statechange_event The statechange event of the MIDIPort interface is fired when a port changes from open to closed, or closed to open. #webdev

🦖 Intl.DurationFormat.prototype.formatToParts() ☑️ Newly available (from Mar 2025) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/formatToParts The formatToParts() method of Intl.DurationFormat instances returns an array of objects […]

🦖 Notification: close event 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/Notification/close_event The close event of the Notification interface fires when a Notification is closed. #webdev

🦖 position-visibility 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/position-visibility The position-visibility CSS property enables conditionally hiding an anchor-positioned element depending on, for example, whether it is overflowing its […]

🦖 XML introduction 🦖 https://developer.mozilla.org/en-US/docs/Web/XML/Guides/XML_introduction XML (Extensible Markup Language) is a markup language similar to HTML, but without predefined tags to use. Instead, you define your own tags designed specifically for your needs. This is a powerful […]

🦖 dynamic-range-limit-mix() 🦖 https://developer.mozilla.org/en-US/docs/Web/CSS/dynamic-range-limit-mix The dynamic-range-limit-mix() CSS function creates a custom maximum luminance limit by mixing different dynamic-range-limit keywords in specified amounts. #webdev #css

🦖 RTCPeerConnectionStats: timestamp property ☑️ Newly available (from May 2023) https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnectionStats/timestamp The timestamp property of the RTCPeerConnectionStats dictionary is a DOMHighResTimeStamp object specifying the time at which the […]

🦖 null ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/null The null keyword refers to the null primitive value, which represents the intentional absence of any object value. #webdev #javascript

🦖 WebAssembly control flow instructions 🦖 https://developer.mozilla.org/en-US/docs/WebAssembly/Reference/Control_flow WebAssembly control flow instructions. #webdev

🦖 border-left ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/border-left The border-left shorthand CSS property sets all the properties of an element's left border. #webdev #css

🦖 <mpadded> ✅ Widely available (from Jan 2023) https://developer.mozilla.org/en-US/docs/Web/MathML/Reference/Element/mpadded The <mpadded> MathML element is used to add extra padding and to set the general adjustment of position and size of enclosed contents. #webdev #mathml

🦖 Error: Permission denied to access property "x" 🦖 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Property_access_denied The JavaScript exception "Permission denied to access property" occurs when there was an attempt to access an object for which you have no […]

🦖 HTMLTableCellElement: abbr property ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/HTMLTableCellElement/abbr The abbr property of the HTMLTableCellElement interface indicates an abbreviation associated with the cell. If the cell does not represent a […]

🦖 UserActivation: hasBeenActive property ☑️ Newly available (from Nov 2023) https://developer.mozilla.org/en-US/docs/Web/API/UserActivation/hasBeenActive The read-only hasBeenActive property of the UserActivation interface indicates whether the current window has sticky user activation. #webdev

🦖 mask-position ☑️ Newly available (from Dec 2023) https://developer.mozilla.org/en-US/docs/Web/CSS/mask-position The mask-position CSS property sets the initial position, relative to the mask position layer set by mask-origin, for each defined mask image. #webdev #css

🦖 DOMRect: y property ✅ Widely available (from Jan 2020) https://developer.mozilla.org/en-US/docs/Web/API/DOMRect/y The y property of the DOMRect interface represents the y-coordinate of the rectangle, which is the vertical distance between the viewport's top edge and the rectangle's origin […]

🦖 Content Security Policy errors and warnings 🦖 https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP/Errors When you see any of the following messages logged in the browser devtools console, it indicates that a problem related to CSP has occurred. #webdev #http

🦖 scroll() 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/CSS/animation-timeline/scroll The scroll() CSS function can be used with animation-timeline to indicate a scrollable element (scroller) and scrollbar axis that will provide an anonymous scroll progress timeline for […]

🦖 Accept-Language header ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Language The HTTP Accept-Language request header indicates the natural language and locale that the client prefers. The server uses content negotiation to […]