Which browser is the best to build an extension on in 2026?

Choosing the right browser to build for in 2026 is less about which one is better and more about where your specific users live. While the technical gap between platforms has narrowed thanks to the universal adoption of Manifest V3, the strategic differences in distribution and developer experience remain significant.

Whether you are aiming for massive scale, deep enterprise integration, or a privacy-first niche, here is how the big three stack up for developers this year. By understanding the unique strengths of each ecosystem, you can decide whether to focus your energy on one primary store or launch across the entire web.

Google Chrome is the Unrivaled King of Distribution

Google Chrome remains the default choice for most developers because of its sheer market dominance and massive reach. In 2026, Chrome still commands a majority of the global browser market share, meaning that a successful launch on the Chrome Web Store provides an immediate path to millions of potential users.

From a technical standpoint, building for Chrome in 2026 means fully embracing the Manifest V3 ecosystem and its event-driven service workers. While the transition was complex, the platform is now highly stable and offers the most advanced side panel APIs in the industry. The developer documentation is extensive, and the sheer volume of users makes it the best place to find a viral audience.

Microsoft Edge is the Enterprise Powerhouse

Microsoft Edge has carved out a unique and profitable niche in the corporate and productivity sectors. Because Edge is the default browser for millions of professional Windows machines, it is the best platform for building tools aimed at B2B workflows and office productivity.

The best part about building for Edge is that it is built on the Chromium engine, just like Chrome. This means that almost any extension you build for Google can be ported to the Microsoft Edge Add-ons store with nearly zero code changes. For developers, this represents a massive opportunity to capture high-value corporate users without any significant extra development work.

Mozilla Firefox is the Privacy-First Innovator

Firefox continues to be the browser of choice for power users, developers, and privacy advocates. While its market share is smaller than its Chromium-based rivals, its user base is exceptionally loyal and often more willing to pay for premium tools that respect their data.

For developers, Firefox offers a unique advantage by maintaining support for both Manifest V2 and V3 in 2026. This makes it the superior choice for building complex content blockers or advanced privacy tools that require more granular control over network requests. The Firefox developer tools are also widely considered to be some of the most robust for debugging complex scripts.

Comparing the Review and Submission Process

When evaluating these platforms, you must consider the human element of the submission and review process. Chrome has the most automated system, which can result in rapid approvals but also sudden, unexplained rejections. Dealing with automated systems requires strict adherence to every single policy detail to avoid being flagged.

Microsoft Edge and Firefox often provide a more transparent review experience compared to the automated nature of Chrome. Firefox in particular is praised for its community-driven approach, where human reviewers often provide direct feedback. Understanding these different review cultures can help you prepare your code and documentation to pass the first time around.

The Strategy of Browser Agnostic Development

In 2026, the smartest move for any developer is to adopt a browser-agnostic development workflow. By writing your code using standard WebExtension APIs, you can target Chrome, Edge, and Firefox simultaneously. This triples your potential reach without significantly increasing your maintenance burden or development time.

Most modern teams start with Chrome as their lead browser for initial testing and then use simple build scripts to generate versions for the other stores. This ensures that you are capturing the high-volume traffic of Google, the corporate users of Microsoft, and the privacy-conscious community of Mozilla. It is the most resilient way to build a long-term software business in the browser.

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Optimizing for the Side Panel Revolution

A major trend in 2026 is the move toward side panel interfaces, which provide a persistent workspace for users. Chrome and Edge have both heavily invested in their Side Panel APIs, allowing extensions to stay open while a user switches between different tabs. This has fundamentally changed how developers think about user retention and engagement.

Firefox has also followed suit by refining its sidebar capabilities to stay competitive with the Chromium browsers. When building your extension, you should design your UI to fit comfortably in these narrow vertical spaces. A well-designed side panel is often the difference between an extension that is used once and one that becomes a permanent part of a user's daily routine.

Leveraging Native AI APIs Across Browsers

In 2026, browsers are competing on their built-in AI capabilities, such as Google’s Gemini Nano and Microsoft’s Copilot integration. As a developer, you can now tap into these local models to provide intelligent features without the cost of external API calls. This is a game-changer for solo developers who want to scale without high infrastructure costs.

While Chrome offers the most direct access to local models, Edge provides deep integration with the broader Microsoft AI ecosystem. Firefox is focusing on privacy-first local AI that ensures no data ever leaves the user's device. Choosing a browser to build on often comes down to which AI ecosystem provides the best tools for your specific features.

Navigating the Security and Permission Landscape

Security requirements have become much stricter across all browsers in 2026 to protect users from malicious code. You must be prepared to justify every permission you request in your manifest file, especially those that allow access to all website data. Browsers now use AI-driven audits to flag extensions that ask for more power than they actually need.

Firefox and Chrome both have different ways of handling how permissions are granted to users. Chrome tends to favor a one-time grant during installation, while Firefox and the newer Manifest V3 standards encourage optional permissions that are granted only when a user triggers a specific feature. Mastering this "just-in-time" permission model is essential for a smooth user experience.

The Importance of Cross Browser Testing Tools

To succeed on multiple platforms, you must invest in high-quality cross-browser testing tools. In 2026, there are specialized environments that allow you to preview your extension in Chrome, Edge, and Firefox simultaneously. This helps you catch tiny CSS bugs or API discrepancies before they reach your users in the real world.

Consistent testing is the only way to ensure that your brand reputation remains high across all marketplaces. A bug that only exists on one browser can still lead to negative reviews that tank your rankings everywhere. By using automated testing suites, you can ship updates with confidence, knowing that your extension works perfectly regardless of which browser the user chooses.

Launch Faster with a Universal Foundation

Building for three different browsers can be a daunting task if you are starting from zero. The most successful developers in 2026 skip the manual setup and use a universal foundation to handle the browser-specific quirks for them. This allows them to focus 100% of their energy on the unique value proposition of their tool.

By using a production-ready boilerplate like ExtensionFast, you get a codebase that is already optimized for Chrome, Edge, and Firefox out of the box. It handles the Manifest V3 configurations, secure authentication, and side panel layouts so you can launch your vision in a single weekend. You can stop worrying about browser compatibility and start finding your first thousand users today.

You can skip the setup and start building your core vision today with ExtensionFast.