🦖 CSSScopeRule ☑️ Newly available (from Dec 2025) https://developer.mozilla.org/en-US/docs/Web/API/CSSScopeRule The CSSScopeRule interface of the CSS Object Model represents a CSS @scope at-rule. #webdev

🦖 TypedArray.prototype.fill() ✅ Widely available (from Sept 2016) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/fill The fill() method of TypedArray instances changes all elements within a range of indices in a typed array to a static value. It […]

🦖 Window: vrdisplaydisconnect event 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/Window/vrdisplaydisconnect_event The vrdisplaydisconnect event of the WebVR API is fired when a compatible VR display is disconnected from the computer. #webdev

🦖 SVGElement: nonce property ✅ Widely available (from Mar 2022) https://developer.mozilla.org/en-US/docs/Web/API/SVGElement/nonce The nonce property of the SVGElement interface returns the nonce that is used by Content Security Policy to determine whether a given fetch will be allowed to […]

🦖 <stop> ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/SVG/Reference/Element/stop The <stop> SVG element defines a color and its position to use on a gradient. This element is always a child of a <linearGradient> or <radialGradient> element. #webdev #SVG

🦖 ValidityState: valueMissing property ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/ValidityState/valueMissing The read-only valueMissing property of the ValidityState interface indicates if a required control, such as an <input>, <select>, or <textarea> […]

🦖 PublicKeyCredential: id property 🦖 https://developer.mozilla.org/en-US/docs/Web/API/PublicKeyCredential/id The id read-only property of the PublicKeyCredential interface is a string, inherited from Credential, which represents the identifier of the current PublicKeyCredential instance. #webdev

🦖 do...while ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/do...while The do...while statement creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated after […]

🦖 HTTP reference 🦖 https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference This page lists HTTP reference documentation on MDN. #webdev #HTTP

🦖 WebGL2RenderingContext: deleteVertexArray() method ✅ Widely available (from Sept 2021) https://developer.mozilla.org/en-US/docs/Web/API/WebGL2RenderingContext/deleteVertexArray The WebGL2RenderingContext.deleteVertexArray() method of the WebGL 2 API deletes a given WebGLVertexArrayObject […]

🦖 CSS animations 🦖 https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Animations The CSS animations module lets you animate the values of CSS properties, such as background-position and transform, over time by using keyframes. Each keyframe describes how the animated element should render […]

🦖 SharedWorker: error event ☑️ Newly available (from May 2026) https://developer.mozilla.org/en-US/docs/Web/API/SharedWorker/error_event The error event of the SharedWorker interface fires when an error occurs in the worker. #webdev

🦖 SourceBuffer: abort event 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/SourceBuffer/abort_event The abort event of the SourceBuffer interface is fired when the buffer appending is aborted, because the SourceBuffer.abort() or SourceBuffer.remove() method is called […]

🦖 GPUCompilationMessage 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/GPUCompilationMessage The GPUCompilationMessage interface of the WebGPU API represents a single informational, warning, or error message generated by the GPU shader module compiler. #webdev

🦖 ServiceWorkerContainer: startMessages() method ✅ Widely available (from Jan 2020) https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/startMessages The startMessages() method of the ServiceWorkerContainer interface explicitly starts the flow of messages being dispatched […]

🦖 Object.prototype.__defineSetter__() 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__ The __defineSetter__() method of Object instances binds an object's property to a function to be called when an attempt is made […]

🦖 ElementInternals: form property ✅ Widely available (from Mar 2023) https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/form The form read-only property of the ElementInternals interface returns the HTMLFormElement associated with this element. #webdev

🦖 Deriving the quadratic formula 🦖 https://developer.mozilla.org/en-US/docs/Web/MathML/Guides/Deriving_the_quadratic_formula This page outlines the derivation of the Quadratic Formula. Nine equations are organized in the <mtable> element to align the steps of the derivation by the equal sign […]

🦖 Vary header ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Vary The HTTP Vary response header describes the parts of the request message (aside from the method and URL) that influenced the content of the response it occurs in. Including […]

🦖 ElementInternals: ariaRowSpan property ✅ Widely available (from Oct 2023) https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/ariaRowSpan The ariaRowSpan property of the ElementInternals interface reflects the value of the aria-rowspan attribute, which defines the number of […]

🦖 autofocus ✅ Widely available (from Feb 2023) https://developer.mozilla.org/en-US/docs/Web/SVG/Reference/Attribute/autofocus The autofocus global SVG attribute defines a focusable element to be focused after it's connected to a document. The attribute has no effect if the element is not […]

🦖 scriptlevel 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/MathML/Reference/Global_attributes/scriptlevel The scriptlevel global attribute sets the math-depth of a MathML element. It allows overriding rules from the user agent stylesheet that define automatic calculation […]

🦖 align-items CSS property ✅ Widely available (from Sept 2015) https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/align-items The CSS align-items property sets the align-self value on all direct children as a group. In flexbox, it controls the alignment of items on the cross […]

🦖 Summarizer: sharedContext property 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/Summarizer/sharedContext The sharedContext read-only property of the Summarizer interface returns a string describing the context the pieces of text to summarize are being used in. This […]

🦖 Access-Control-Allow-Origin header ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Origin The HTTP Access-Control-Allow-Origin response header indicates whether the response can be shared with requesting code from […]

🦖 AnalyserNode: smoothingTimeConstant property ✅ Widely available (from Jul 2015) https://developer.mozilla.org/en-US/docs/Web/API/AnalyserNode/smoothingTimeConstant The smoothingTimeConstant property of the AnalyserNode interface is a double value representing the averaging constant with the […]

🦖 400 Bad Request 🦖 https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/400 The HTTP 400 Bad Request client error response status code indicates that the server would not process the request due to something the server considered to be a client error. The reason for a 400 […]

🦖 js13kGames: Progressive loading 🦖 https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/Tutorials/js13kGames/Loading In previous steps of this tutorial, we covered APIs that help us make our js13kPWA example a Progressive Web App using Service Workers, Web Manifests, and […]

🦖 ARIA: aria-expanded attribute 🦖 https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Reference/Attributes/aria-expanded The aria-expanded attribute is set on an element to indicate if a control is expanded or collapsed, and whether or not the controlled elements are displayed or […]

🦖 USBDevice: clearHalt() method 🟧 Limited availability https://developer.mozilla.org/en-US/docs/Web/API/USBDevice/clearHalt The clearHalt() method of the USBDevice interface returns a Promise that resolves when a halt condition is cleared. A halt condition is when a data transfer to or from […]