Firefox 153 release notes for developers (Beta)

Changes for web developers

JavaScript

• The TC39 Intl.Locale info proposal is now supported. This includes all the instance methods on Intl.Locale that are prefixed with "get" — getCalendars(), getCollations(), getHourCycles(), getNumberingSystems(), getTextInfo(), getTimeZones(), and getWeekInfo(). (Firefox bug 2037069).
• The Error.stackTraceLimit static data property is supported for setting or getting the maximum number of stack frames captured in an error stack trace. Setting the value smaller than the default can improve performance. (Firefox bug 2037856).

APIs

Media, WebRTC, and Web Audio

• The RTCDtlsTransport.getRemoteCertificates() method gets the certificates used by the remote peer to secure the DTLS communication. These can be used for application-layer authentication of a remote peer. (Firefox bug 1805446).
• The decodingInfo() and encodingInfo() methods of the MediaCapabilities interface now accept the "webrtc" configuration type. This allows a site to query whether a given audio or video configuration can be decoded or encoded using WebRTC, and whether doing so will be smooth, power efficient, or both. Support for the non-standard transmission type, which was used as an alias for webrtc, is removed. (Firefox bug 2037610 and Firefox bug 2032075).

Changes for add-on developers

• Extensions now require explicit user permission to access file:// URLs. Previously, access to local files was covered by the "Access your data for all websites" host permission. This change introduces a separate "Access local files on your computer" option in the extension's permissions settings (desktop only), and file access is turned off by default for all extensions, including existing ones. The extension.isAllowedFileSchemeAccess() method now correctly returns true if the user has granted file scheme access; previously, Firefox always returned false. Additionally, calling devtools.inspectedWindow.eval() on file:// URLs now requires this permission. (Firefox bug 2034168)
• Supports the userScripts.execute() method, enabling extensions to inject user scripts on demand into a tab or frame. Unlike userScripts.register(), this method supports one-off injection of multiple script sources executed in a defined order. (Firefox bug 1930776)
• Adds the publicSuffix API, enabling extensions to determine the registrable domain (eTLD+1) and public suffix of a hostname using the browser's built-in Public Suffix List. The API provides three synchronous methods: publicSuffix.isKnownSuffix(), publicSuffix.getKnownSuffix(), and publicSuffix.getDomain(). (Firefox bug 1315558)
• Extension content scripts can now read and modify constructed stylesheets in document.adoptedStyleSheets and ShadowRoot.adoptedStyleSheets, without .wrappedJSObject. (Firefox bug 1751346)
• Adds documentId to a range of WebExtension APIs, including a new runtime.getDocumentId() method, webNavigation events and methods, webRequest events, scripting injection targets, and messaging APIs. See Work with documentId for the full list of supported events and methods, along with guidance on using documentId. (Firefox bug 1891478)
• For contextual identities (containers):
  • Adds the contextualIdentities.getSupportedColors() and contextualIdentities.getSupportedIcons() methods to retrieve the supported colors and icons, avoiding the need to hardcode those values. (Firefox bug 2044712)
  • Updates the colors available. "turquoise" is renamed to "cyan", "toolbar" is renamed to "gray", and "violet" is added. The legacy names "turquoise" and "toolbar" are accepted for backward compatibility. To avoid hardcoding color names, use contextualIdentities.getSupportedColors() to retrieve the available colors. (Firefox bug 2044354)

Experimental web features

These features are shipping in Firefox 153 but are disabled by default. To experiment with them, search for the appropriate preference on the about:config page and set it to true. You can find more such features on the Experimental features page.