ompatibility testing proves your software works properly across different browsers, devices, operating systems, and networks – catching problems before users find them.

Say your app works beautifully on Chrome running on your MacBook. It looks perfect, responds instantly and handles everything you throw at it. Then a customer tries it on Firefox on Windows 10 and half the buttons don't work. Someone else then opens it on Safari on their three-year-old iPad and it crashes on load. And finally, another person on a spotty mobile connection gets stuck on a loading screen that never ends. What’s going to happen to those users? They get frustrated, give up, and never come back.

Compatibility testing catches these problems while you can still fix them cheaply – and before they turn into angry support tickets, one-star reviews, and lost revenue.

What is compatibility testing?

Simply put, compatibility testing gives peace of mind that your software performs as it should across:

• Browsers - Chrome, Firefox, Safari, Edge and their versions
• Operating systems - Windows, macOS, Linux, iOS, Android
• Devices - phones and tablets
• Networks - different connection speeds and reliability
• Hardware - various processors, memory, graphics cards

The goal of compatibility testing is to find configuration-specific issues before your users do.

Why does compatibility testing matter?

Because your users aren't all running the latest MacBook Pro with gigabit fiber. Real users are running older browser versions (because updating is a hassle), using varied screen sizes (from phone to ultrawide monitor), dealing with unreliable mobile connections (because they're on a train or in a coffee shop), and working with whatever hardware they have (not everyone upgrades every year).

Skip compatibility testing and you'll discover issues the expensive way through customer complaints, support tickets, and the users who don't complain but quietly switch to your competitor.

What types of compatibility testing should you do?

There are five main types of compatibility testing. Pick the ones that matter for your product and who uses it:

Browser compatibility testing

Chrome, Firefox, Safari, and Edge all render websites differently. What works perfectly in one can break spectacularly in another. Focus on browsers your users actually use by checking your analytics. Test current versions plus one or two back. If your analytics show 2% of traffic from Opera Mini, skip it.

Device compatibility testing

Smartphones, tablets, desktops – each brings headaches around screen sizes, touch vs mouse, processing power, and memory. Focus on responsive design that actually works, touch interactions that feel right, and performance on older hardware.

Operating system compatibility testing

Windows, macOS, Linux, iOS, Android – each has its own ideas about file paths, permissions, fonts, and resources. Common issues: Windows loves backslashes while everyone else uses forward slashes, permission models that work completely differently, fonts that render inconsistently.

Network compatibility testing

Test how your app handles slow connections (3G that feels like dial-up, coffee shop WiFi), network interruptions, proxy configurations, and geographic restrictions.

Hardware compatibility testing

Different processors, graphics cards, memory, and connected devices like printers or webcams. Matters most for apps that need serious power, software that connects to physical equipment, or tools with minimum specs your users need to meet.

Read more: Hardware compatibility testing

What tools help with compatibility testing?

The right tools give you access to the conditions your users actually experience. Here's what works, depending on what you're testing:

Browser testing services - BrowserStack, Sauce Labs, and LambdaTest are cloud platforms that let you test on hundreds of real browsers and devices without owning them. You can test on Safari 12 on an iPhone 8, Chrome 95 on Windows 10, or whatever specific combination your users run. Not cheap (plans typically start around $30-40/month), but cheaper than production bugs.

Device emulation - Emulation means one thing pretending to be another thing. Browser dev tools (built into Chrome, Firefox, Edge) let your desktop browser pretend to be a phone or tablet. Click a button and your browser window resizes to match an iPhone screen, mimics touch interactions, and identifies itself as a mobile device. Good for checking things fast while you're building, but don't rely on them for final testing – emulation misses subtle rendering issues, touch behavior quirks, and real device performance. It's a simulation, not the real thing.

Network simulation - Tools like browser dev tools, Charles Proxy, and Network Link Conditioner artificially slow down your internet connection so you can see how your software handles slow networks or spotty connections. For realistic testing though, actual networks behave differently than simulated ones.

Virtual machines - VirtualBox or VMware let you run Windows, Linux, or older OS versions on your computer as if they were separate machines. Useful when you need to verify behavior on specific OS versions (like Windows 7 for legacy enterprise users), but they eat up memory and processing power - overkill for simple browser testing.

Real devices - Keep a few physical devices around for critical testing. Nothing replaces actually using a phone or tablet, especially for touch interactions, performance, and visual checks. Start with whatever's most common in your user analytics.

Most teams use different tools at different times – quick checks while building, then broader testing across more combinations, then hands-on checks with real devices before shipping.

How does compatibility testing fit into your release process?

Compatibility testing works best in stages – quick checks early, thorough testing before shipping, and watching for problems after launch. Here's when to test what:

During development - Test in your main browser plus one other and a mobile view and catch obvious problems early before they're built into your code. If something breaks on Firefox while you're building it in Chrome, fix it now rather than discovering it later.

Before release - Run through your full list of browsers and devices. Check the basics everywhere (does it load? does it work?), test everything thoroughly on your most common setups, and do focused checks on less common ones. This is where you catch unusual problems before users do.

After release - Watch support tickets, error tracking tools like Sentry or Rollbar, and analytics for strange patterns. Real-world usage always surfaces unexpected combinations – that one user on Safari 14 with an ad blocker and VPN who finds the bug nobody else hit. Use what you learn to update what you test next time.

New to compatibility testing and don’t know where to start?

If you're not doing any compatibility testing yet, don't try to test everything at once. Start with what your users actually use. Check your analytics for the top 3-5 browser and device combinations. Test those manually before each release. When you find issues, write them down – which browser, which feature, what broke. Over time, you'll spot patterns in what tends to break and where.

As you get comfortable, gradually add more combinations. Maybe you started testing Chrome and Safari on desktop – add mobile. Then add Firefox. Then older versions. Build up your testing as you learn what matters for your users. What matters is understanding how your software behaves in the real world and catching issues that would annoy users. Start with basic coverage, find problems that matter, evolve as you learn what breaks.

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