Chrome, Firefox, Edge and Safari each run their own store with their own review, so reaching all four means four submissions. This guide covers what to change when you port, and what each store asks for.
Port once, then fix the differences
The major browsers use the same extensions API, with differences. MDN lists what to handle when you target several: the API namespace, asynchronous APIs, API coverage, content script contexts, background code and manifest keys. Firefox accepts the chrome namespace but prefers browser with promises, and MDN points to a polyfill for Chrome versions without it. Chrome’s Manifest V3 runs a service worker while Firefox runs scripts, so list both in the background key. Microsoft says a Chrome port to Edge needs minimal changes.
- For Edge, remove update_url from the manifest and rebrand any “Chrome” in the name or description; Microsoft says the rebrand is needed to pass certification.
- MDN says a static manifest per browser is usually the simplest approach, since manifests change little between releases.
Sources: MDN: Build a cross-browser extension · MDN: manifest.json background key · Microsoft Edge: Port a Chrome extension
Firefox: AMO listing, source code and data consent
List on addons.mozilla.org or self-distribute a signed file. Upload a zip, xpi or crx up to 200 MB, write a summary of up to 250 characters and pick up to two Firefox categories. If your code is minified or otherwise hard to read, upload a source package. After validation the add-on is published, but it can still be reviewed later. Since 3 November 2025, new extensions must state what data they collect or transmit, using Firefox’s built-in consent system.
Sources: Extension Workshop: Submitting an add-on · Extension Workshop: Creating an appealing add-on listing · Extension Workshop: Built-in consent for data collection
Firefox’s Recommended Extensions program
Mozilla staff curate Recommended extensions and ask four questions: does it work at an exemplary level, is it safe, is the experience exceptional, and is it relevant to a general, international audience. Developers must follow AMO’s policies, fix bugs promptly and polish the experience with staff. The collection is meant to stay fairly fixed. You can nominate an extension, even your own, by emailing amo-featured at mozilla dot org with the AMO listing link and a short explanation.
Source: Extension Workshop: Recommended Extensions program
Edge Add-ons: free to join, up to seven business days
Microsoft charges no registration fee. You register through Partner Center with a Microsoft account, upload the zip, choose Public or Hidden visibility and complete the privacy page. The store description needs 250 to 10,000 characters and the logo should be 300x300 (128x128 minimum). The 440x280 and 1400x560 tiles and up to six screenshots are optional. Notes for certification can carry test accounts. Microsoft says certification can take up to seven business days after you submit.
Sources: Microsoft Edge: Publish an extension · Microsoft Edge: Register as an extension developer
Safari: ship through the App Store
Safari web extensions ship inside a macOS or iOS app, so you need Apple Developer Program membership and App Review. Package your existing files with xcrun safari-web-extension-packager (formerly safari-web-extension-converter), or use the web packager in App Store Connect, which needs no Mac or Xcode, then test with TestFlight. Guideline 4.4 says extensions may not include marketing, advertising or in-app purchases, and Safari extensions should not claim access to more websites than they need.
Sources: Apple: Packaging a web extension for Safari · Apple: Packaging and distributing with App Store Connect · Apple: App Store Review Guidelines
Vivaldi and Opera: two Chromium routes
Vivaldi’s help says extensions from the Chrome Web Store can be installed in Vivaldi, though some behave differently, so Vivaldi users can install your Chrome listing. Opera runs its own catalogue: you upload through its extensions repository, moderators test the extension against acceptance criteria, and an outstanding one may be placed in a Recommended section. Opera’s guidelines prefer a 612x408 screenshot, with 800x600 as the maximum.
Sources: Vivaldi Help: Using extensions · Opera Help: Publishing guidelines
Facts checked Oct 9, 2026 against the sources linked in each section.