Cross-Browser Extension Development: Chrome vs. Firefox vs. Edge

Meta Title: Cross-Browser Extension Development Guide 2026

Meta Description: Can one codebase power Chrome, Firefox, and Edge extensions? Learn where APIs align, where they break, and when to hire a Chrome extension development company.

Your Chrome extension works. Users like it. Then someone asks: "Does this work on Firefox? What about Edge?"

The honest answer is usually "sort of." Chrome, Firefox, and Edge all support browser extensions, and they share enough DNA that a single codebase sounds possible. Sometimes it is. But the gaps between browsers are specific enough that ignoring them leads to extensions that install fine and then break in ways that are hard to reproduce.

This is the real question behind cross-browser chrome extension development: not whether you can share code, but how much code you can actually share before browser-specific behavior forces you to fork.

All three browsers build on the WebExtensions API. Chrome popularized it. Firefox adopted it. Edge, after Microsoft switched to the Chromium engine in 2020, inherited it almost wholesale.

At the surface level, this means your manifest.json, content scripts, popup pages, and basic storage APIs look nearly identical across all three. A simple extension that injects CSS or reads page content can often run on Chrome, Firefox, and Edge with minimal changes.

The divergence starts below the surface: background execution models, network request interception, permissions handling, and how aggressively each browser terminates idle processes. These are the places where "write once, run everywhere" breaks down.

Manifest V3 Implementation Differences

Chrome enforces Manifest V3 fully. Background pages are gone, replaced by service workers that start, run, and terminate on Chrome's schedule. Firefox supports Manifest V3 but with its own interpretation. Firefox's service worker termination behavior differs from Chrome's, which means state management code that works perfectly in Chrome can fail intermittently in Firefox.

Edge follows Chromium closely and generally accepts V3 extensions that pass Chrome's review. But "generally" is doing heavy lifting in that sentence. Edge has its own store policies, its own review cycle, and occasional rendering differences in extension popups.

The declarativeNetRequest Split

Chrome replaced the blocking webRequest API with declarativeNetRequest, which uses static JSON rules instead of runtime interception. Firefox still supports some webRequest functionality that Chrome has deprecated. If your extension does anything with network filtering (ad blocking, security monitoring, content modification), this difference matters more than everything else combined.

Building cross-browser network interception requires either maintaining two code paths or limiting yourself to the lowest common denominator, which usually means Chrome's more restrictive model.

Storage and Permissions

The chrome.storage and browser.storage APIs are functionally similar but not identical. Firefox uses a browser namespace with Promise-based APIs by default. Chrome uses callback-based APIs under the chrome namespace, though modern versions support Promises too. Edge follows Chrome's conventions.

The practical fix is a polyfill or a thin abstraction layer. Mozilla's webextension-polyfill library handles most of these namespace differences. It is well-maintained and widely used in production cross-browser builds.

A single codebase works well when your extension meets these conditions: it primarily uses content scripts and popup UI, it does not intercept network requests dynamically, it stores data using standard storage APIs, and it does not depend on browser-specific features like Chrome's side panel API or Firefox's container tabs.

Productivity tools, form fillers, page annotators, and UI customization extensions are good candidates for this approach. The core logic stays in shared modules. Browser-specific configuration goes into separate manifest files or build-time flags.

Teams building with chrome extension development frameworks like WXT, Plasmo, or manual Vite setups can configure build targets per browser while keeping a single source tree. TypeScript helps here. Type checking catches API mismatches at build time rather than in production.

A SaaS company that recently needed an internal tool for browser-based data capture started with Chrome, validated the product with users, then extended to Firefox and Edge using a shared TypeScript codebase with per-browser manifest files. The core logic (content script injection, popup state management, API communication) stayed identical. The only browser-specific code was the background service worker configuration and a Firefox-specific workaround for storage event timing.

Some extensions genuinely need separate codebases per browser. Security tools that intercept and filter network traffic hit the declarativeNetRequest vs webRequest split hard. Extensions that use Chrome's enterprise policy APIs for managed deployments have no Firefox equivalent. Extensions built around Chrome's side panel or Firefox's container tabs API are browser-specific by definition.

Enterprise IT tools are the most common case. A company deploying a custom Google Chrome plugin for internal security monitoring will likely need a fundamentally different architecture for Firefox, if Firefox support is even required. Chrome extension development outsourcing for these projects should include explicit cross-browser scoping during the requirements phase, not as an afterthought.

Here is what a working cross-browser development workflow actually looks like.

Start with Chrome. Chrome has the largest extension user base, the most mature tooling, and the most documentation. Get the extension working, tested, and published on the Chrome Web Store first. This is your reference implementation.

Use a build tool that supports multi-target output. WXT and Plasmo both support Chrome, Firefox, and Edge targets from a single source tree. Your chrome extension development with react or chrome extension development typescript setup should produce separate build artifacts per browser from the same source.

Isolate browser-specific code behind interfaces. Network interception, notification handling, and background worker configuration should live behind abstraction layers. The implementation behind each interface can vary per browser without touching shared business logic.

Test on real browsers, not just the APIs. Firefox's extension debugging tools behave differently from Chrome's DevTools. Edge's popup rendering has its own quirks. Automated testing catches API-level issues, but manual testing on each target browser catches visual and behavioral differences that unit tests miss.

Publish to each store separately. Chrome Web Store, Firefox Add-ons (AMO), and the Microsoft Edge Add-ons store each have their own review process, listing requirements, and approval timelines. Budget time for each.

MetaDesign Solutions provides custom chrome extension development services with explicit cross-browser support built into the project scope from day one. The team architects shared-core codebases with browser-specific adapters for network interception, storage, and background execution.

For enterprise teams evaluating whether to hire chrome extension developer or build in-house, the cross-browser question is a good litmus test. If your internal team has shipped V3-native extensions on Chrome but has not tested against Firefox's worker termination behavior or Edge's store review process, the cross-browser work alone may justify bringing in specialists.

MetaDesign Solutions has shipped Manifest V3 extensions for enterprise clients across the US, Australia, and India, with cross-browser compatibility as a standard deliverable rather than an add-on.

One codebase can work for many extensions. Three codebases are sometimes unavoidable. The deciding factors are network interception requirements, browser-specific API usage, and enterprise deployment constraints.

The best approach is to start with Chrome (where the users and the tooling are), build with cross-browser compatibility in mind from the start, and isolate browser-specific code behind clean interfaces. Do not treat Firefox and Edge support as a port you will do later. The architectural decisions that make cross-browser support expensive happen in the first week of development, not the last.

Need cross-browser extension development done right the first time?Talk to MetaDesign Solutions and get a technical assessment within five business days.