Answer.

Background

The variety of browsers leads to differences in the display and functionality of websites. The reliability of the frontend depends on the correctness of the execution of basic scenarios in different browsers, especially if the product is aimed at a wide audience.

Problem

Quickly checking all target configurations is difficult. Non-obvious bugs often appear only in certain versions of browsers or operating systems. Overlooking such defects affects user loyalty.

Solution

Manual cross-browser testing starts with selecting the necessary browsers (e.g., Chrome, Firefox, Edge, Safari) and their current versions. The following is tested:

Layout and display of elements.
Functionality of forms and dynamic components.
Interaction with extensions and scripts.

Documentation of the found bugs is important, with precise indications of the browser, version, and reproduction steps.

Key features:

One should not rely only on the most popular software; less common browsers and mobile platforms should also be included.
It is essential to pay attention to non-obvious defects (rendering differences, event handling, css/js behavior).
Remote testing tools (Browserstack, SauceLabs) should be used if there is no physical access to all devices.

Tricky Questions.

If the site works correctly in the latest version of Chrome, will there be problems in Safari or Edge?

Yes, there can be. Each browser may implement standard support differently, especially related to css rendering, javascript behavior, and features of network requests.

Can testing be limited to just one operating system?

No. Even the same browser on Windows and macOS behaves differently, as the OS influences rendering and event handling.

Is visual inspection of the page sufficient?

No. Non-obvious bugs may be related to data processing, caching information or cookies, as well as interaction with APIs.

Typical Mistakes and Anti-Patterns

Assessing only the visual aspect without checking usage scenarios.
Testing only on the main platform (e.g., only on Windows + Chrome).
Lack of detail in bug reports by browser and version.

Real-Life Example

Negative Case

The tester checked the site only in Chrome on desktop, ignoring behavior in mobile browsers and Safari.

Pros:

Quick passing of basic smoke tests.

Cons:

Missed a critical bug with form display on iPhone.
Loss of customers using other platforms.

Positive Case

The tester used Browserstack, checking the site on major desktop and mobile browsers, documenting the steps and taking screenshots of any discrepancies.