Let your analytics drive your testing matrix. If 85% of users are on Chrome and Safari, start there. Test edge cases on Firefox and legacy browsers based on your actual user base, not assumptions.
Strong answers cover: using analytics data to identify the most common browsers and devices, creating a prioritised testing matrix, using cloud testing platforms (BrowserStack, Sauce Labs), automating critical paths across browsers, and manual testing for visual and interaction differences. Best candidates discuss when cross-browser issues are most likely (CSS, JavaScript APIs, form handling).
Practical testing skill. Testing every browser equally is inefficient. Candidates who use data to prioritise their testing matrix are pragmatic and efficient.