Cross browser testing takes minimal effort when you test only the browsers, operating systems, and devices your audience actually uses. Google Analytics and GS StatsCounter report the browser and device mix of real visitors, and testing that shortlist from the least used browser upward clears shared bugs earlier. This guide covers why manual testing stays necessary for cross browser compatibility, the primary objectives of cross browser testing, how to identify browser, OS, and device combinations, preliminary research, customer analytics, the browsers that matter most, and how AI coding agents change the work.
Test on Browsers that 'matter the most'
Though popular browsers (Google Chrome, Mozilla Firefox, Safari, Opera, Yandex, and Microsoft Edge) are available for different operating systems and devices, it is rare that you come across 'browser issues' that are largely dependent on the operating system. Unless the browser code/design goes through a major overhaul, there is a minor difference between two consecutive versions of the same browser. While gathering information about browser statistics to decide on your cross browser testing needs, it makes sense to combine all the desktop versions of one browser into a single row of your matrix.
Internet Explorer no longer earns a row in that matrix. Microsoft ended support for the Internet Explorer 11 desktop application on June 15, 2022, and the app is permanently disabled on the affected versions of Windows 10, as the Microsoft lifecycle FAQ records. Sites that still depend on legacy rendering run through Internet Explorer mode inside Microsoft Edge, which Microsoft has committed to supporting through at least 2029. If your analytics still report Internet Explorer traffic, test that path in Edge with IE mode turned on instead of keeping a separate legacy browser in the shortlist.
The argument discussed above also holds good for mobiles & tablets. Handheld devices have been on the rise and mobiles are one medium that can no longer be ignored. In fact, many organizations are working on mobile friendly websites with a mobile-first agenda. Along with the popular browsers, many devices have in-app browsers e.g. Samsung Internet in Samsung devices, Mi Browser in MI devices, etc. In order to gain market share, device manufacturers make their in-house developed 'native browsers' as the default browser and many times, these in-app browsers become more important from cross-browser testing perspective than other popular browsers as you are targeting the customer base of the entire mobile company itself.
Hence, based on the market being targeted and the priority of the medium (mobile, tablet, desktop, etc.), you should have an organized and prioritize testing conducted on browsers that are popular in your target market. GS StatsCounter can give you detailed information about the browser market share from a 'region' & 'device' perspective. Pull that report for the regions you actually sell into, and rebuild the shortlist whenever the mix moves.
Vendor browsers that ship as the default on Android handsets, such as Samsung Internet, take a real share of that traffic in several regions, so the web developers & test team should spend their development & testing effort on the browsers that matter the most for the product.
Along with the details about browser usage statistics, you should also have a detailed view about 'test priorities of the browsers'. This would help in prioritizing the cross-browser testing & development effort. For example, if only a small percentage of your website visitors use Opera, testing on Opera should be a lower priority than other browsers which are used by a majority number of users who use your web-app/website. However, it is crucial to include those low priority browsers in your testing checklist, as they may bring your power leads.
Now that we have touched upon some of the basic elements to make your cross-browser testing efficient, let's look at the points in more detail.
1. Focus on bugs which are 'not browser dependent'
Before the source code is pushed to the Development environment/dedicated QA testing environment/Production environment, you should make perform a 'regression testing' on the 'browser of your choice' or the browser that you use frequently for browsing. The primary advantage of following this approach is the testing would be performed on a latest browser (as by default 'auto-update' is enabled in all the browsers) and the focus would be to 'unearth bugs & fix bugs' that are browser agnostic. There might be cases that your website/web-app is not rendering correctly on certain browsers/devices, but the issue might not be related to the viewport or screen-size of the device. It could be a bug that could be browser-agnostic and spending too much time on 'testing the functionality on a certain device/browser category' could hamper the speed of the product development.
Some pointers to figure out browser-agnostic bugs are
- Check whether the website renders properly after disabling CSS and JavaScript from the code.
- Use browser developer debug options to view the website/web-app for different viewports.
- Try testing 'interactive use cases' on the website/web-app.
- Check whether the web-app/website works fine in scenarios where there is throttling of internet speeds. You could even use the admin login of your ISP (Internet Service Provider) to limit the internet speed. There are online tools (like webpagetest, etc.) that can also be used in order to test this scenario.
2. Achieve maximum testing throughput by focusing on the 'RIGHT Browsers'
The approach mentioned in step (1) would be useful in unearthing bugs that are browser agnostic, but the cross browser testing would anyways be performed on 'one of the popular browsers' that is installed on the developer's machine. There is a possibility of a regression defect i.e. a fix that was made for a particular browser might result in breakage of functionality on some other browser e.g. Fixing an issue that occurred on Chrome might result in a side-effect for Safari or any other browser. Another possibility is that a fix on one browser could fix the issue on all the other browsers.
When the test team reports a bug, they would also mention the 'browser on which the issue occurred', along with the scenario. Based on the bug-pattern, the development team can come up with a table that lists the browsers based on the 'Risk v/s Returns' matrix where 'Risk' indicates the impact of a bug-fix on cross browser compatibility that one type of browser may have on other browsers on which the testing is performed. Browsers can be categorized in different levels (risk-1, risk-2, risk-3) where risk severity rises with each level and 'Returns' would indicate the impact of a bug-fix (across different browsers).
You either have the option to test on the browsers in the risk-1 -> risk-2 -> risk-3 -> risk-nth order (ascending) or risk-nth -> risk-3 -> risk-2 -> risk-1 (descending). In the first approach, the testing would be performed on popular browsers first, whereas in the second approach; the testing would be performed on 'less popular browsers' first. The approach-2 has better throughput (both in terms of development & testing) since bugs that are encountered (and fixed) for 'less popular browsers' would also result in fixing similar issues for 'popular browsers'. CanIUse is one popular website that can help you in identifying browsers on which your website/web-app might encounter maximum number of issues with respect to the feature provided through your web elements. This finding should be used in conjunction with the data that we got from the section titled Identification of Browser, OS, and Device combinations.
Feature support data now comes in a second form that cuts the matrix further. The WebDX Community Group publishes Baseline, a support status that every web feature carries against a fixed core browser set: Chrome on desktop and Android, Edge on desktop, Firefox on desktop and Android, and Safari on macOS and iOS. A feature marked Newly available works in the latest stable release of every browser in that set. A feature marked Widely available has held that support for 30 months, so older installs handle it too. Read the Baseline status before you write the test plan, because a feature that is already Widely available rarely needs its own cross browser pass, and the features still at Limited availability are where your test effort belongs.
As far as cross-browser testing is concerned, verification of the functionalities on different browsers & different screen sizes (and viewports) is considered an ideal option. By doing so, you can maximize your testing efforts since your website/web-app has been through a gruelling phase of cross browser testing (on combinations of different kinds of browsers, devices, as well as the operating system).
3. 'Last-mile' testing
By following the steps mentioned in (1) & (2), the majority of the bugs would have been unearthed & fixed as well. It is mandatory that a sanity test is performed on these set of browsers after each development & test cycle. Many mobile devices have native in-app browsers, some browsers follow a 'freemium business model' (i.e. some browser features are free, some are premium), whereas some browsers are not updated regularly. Such kind of browsers are 'low priority browsers' since only a minuscule percentage of users might be using them, hence you should test on these browsers only when you are done testing on all the other browsers.
Since the gains that you get by testing on these low priority browsers, sanity testing on these browsers should be done if your test resources have time.
4. Test before you go live
It is always recommended that extensive cross-browser testing is performed before making your website/web-app live in the Production environment. With the trend of "Shift-Left" Testing, it becomes imperative to test early and test often. You can perform cross browser testing of your locally hosted website or web-pages using an local page testing hosted through TestMu AI cloud servers. This is essential to provide a quality user-experience since the first experience makes a lot of difference.
5. Take care about Accessibility
In order to take care of the 'Accessibility Factor', you should answer the important question - 'Can everyone use your website/web-app?' i.e. Can a person with hearing impairment/colour blindness/motor impairments/some other disability use your product? It is indispensable to have the product tested for cross browser accessibility testing.
Key Takeaway: Testing the browsers that matter most means ranking them by real market share, fixing browser-agnostic bugs first, then working from the least popular browsers up to the most popular so one fix clears the same issue elsewhere.
How do AI coding agents change cross browser testing?
AI coding agents can now drive a real browser themselves, so an agent can open a page, reproduce a rendering bug and write the check for it. The agent does not decide which browsers you cover. That decision still comes from your analytics and the shortlist you built from it. Microsoft publishes Playwright MCP, a Model Context Protocol server that gives an LLM browser automation through Playwright. Its README states that it works from structured accessibility snapshots and bypasses the need for screenshots or visually-tuned models. Its browser option accepts chrome, firefox, webkit and msedge, so an agent wired to it can reach all three major rendering engines.
The agent tool you connect decides your engine coverage, and most of them cover one engine. The Chrome DevTools team publishes chrome-devtools-mcp, which lets a coding agent control and inspect a live Chrome browser. Its own documentation says it officially supports Google Chrome and Chrome for Testing only, and that other Chromium-based browsers may work but are not guaranteed. A clean agent session on that server tells you nothing about Gecko or WebKit. Treat it as a debugging aid for one engine, not as a cross browser pass.
Read the engine caveat before you trust an agent run as coverage. The Playwright browsers documentation says its WebKit build is derived from the latest WebKit main branch sources, often before those updates reach Apple Safari, and that its Firefox build does not work with the branded Firefox release because it relies on patches. A green agent run on Playwright WebKit is evidence about the engine, not proof about the Safari version your users have installed. Let the agent cut the cost of writing and re-running the checks. Keep the cost of deciding what to check where it belongs, with your usage data.
Key Takeaway: An AI coding agent can drive a real browser and write the check, but the browser automation tool it connects to sets the engine coverage, so a Chrome-only agent server proves nothing about Gecko or WebKit.
Summary - In order to get the best out of cross-browser testing, it is essential that you:
- Device a cross browser testing strategy.
- Create a cross browser compatibility matrix.
- Prioritize browsers so that testing is performed on 'browsers that yield the best results'.
- Keep in mind the accessibility as well as the usability.
- Keep in mind the browser-dependent bugs.
- Perform local testing of your web-pages or website before you push them on the internet.
- Use a cloud-based, cross browser testing tool like TestMu AI to cherish the maximum result with minimum efforts. These tools will provide you a hassle free VM setup through their library of legacy as well as latest browsers running across multiple androids, iOS, MacOS or Windows devices.