Answer.

Manual compatibility testing is the process of checking how software operates in various environments (for example, different operating systems, browsers, mobile devices) to ensure that it functions correctly for all target users.

Background: With the development of technologies and the increasing number of platforms and devices, it has become standard to check whether an application works equally on Windows and Mac, Android and iOS, Chrome and Firefox. Insufficient attention to compatibility in the past has led to loss of user share and business losses.

Problem: The main challenge is the huge number of possible environment combinations: browser versions, operating systems, resolutions, interface languages. Testing them all is impossible, but missing critical cases leads to situations where the product does not work for some users.

Solution: Implement strategic testing based on:

Analyzing real user statistics (Google Analytics, Yandex.Metric, Mixpanel, etc.) to identify top platforms/devices.
Combining smoke and target scenarios on key combinations of platforms.
Documenting identified incompatibilities with full environmental descriptions.

Key features:

Testing should focus on real user scenarios on target devices.
It is important to document the entire environment: operating system, language, resolution, browser, software version.
Often, it is necessary to use emulators and physical devices simultaneously.

Trick questions.

Is it enough to test only the latest versions of browsers and operating systems?

No! Real users often use outdated software (for example, IE11 or old Android), so compliance with only new versions can lead to missed critical bugs.

Can testing on real devices be replaced by testing in emulators?

No. Many bugs only manifest on real hardware (issues with memory, acceleration, touch, etc.), emulators are only partially effective.

Are all compatibility issues fatal for release?

Not necessarily; some can be considered known limitations — it is important to objectively assess business risks and the density of the user audience for such a combination.

Common mistakes and anti-patterns

Testing only in a standard environment, ignoring other popular platforms.
Failing to retain information about the reproduction environment.
Full reliance on emulators without physical control.

Real-life example

Negative case

A store released a mobile app and tested only on Android 11-12 emulators with Google Pixel. A week later, negative feedback began to pour in from users on Xiaomi and Samsung with older OS versions — the app wouldn't open.

Pros:

Quick verification of core scenarios.

Cons:

Significant combinations of devices and versions were missed.
Increased negative feedback and loss of loyal audience.

Positive case

Before release, the team selected a range of popular devices and browsers, key scenarios underwent iteration on each, and bugs were formalized and prioritized with product management.