Firefox 153 release notes for developers (Nightly)

Changes for web developers

WebAssembly

• JavaScript Promise Integration (JS-PI) is now enabled, allowing WebAssembly modules to interoperate with asynchronous, Promise-based JavaScript APIs. This lets WebAssembly code suspend while waiting for a JavaScript promise and resume when the promise settles. See WebAssembly.Suspending for an explanation and working example. (Firefox bug 2044809).

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 the contextualIdentities.getSupportedColors() and contextualIdentities.getSupportedIcons() methods to retrieve the colors and icons available for contextual identities (containers). (Firefox bug 2044712)

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.