How to Test Cross-Browser Compatibility in Vibecoded Apps

Check your analytics to determine which browsers your users actually use. For most apps, Chrome, Safari, and Firefox cover 95% of traffic. Safari is especially important because it runs on all iPhones — even Chrome on iOS uses Safari's rendering engine under the hood. If your audience skews toward enterprise, Edge and Internet Explorer may also matter.

Set up a testing matrix that covers your top browsers on both desktop and mobile. At minimum, test Chrome desktop, Safari desktop, Safari iOS, Chrome Android, and Firefox desktop. Services like BrowserStack or LambdaTest let you test on browsers and devices you do not own locally.

CSS is the most frequent source of cross-browser issues. Features like gap in flexbox, backdrop-filter, and container queries have varying support. AI tools often use the latest CSS features without fallbacks. Check caniuse.com for any CSS property you are unsure about and test visually in each browser.

JavaScript API differences cause subtle bugs. Safari is notably behind on APIs like Notifications, Web Push, and certain Intl methods. AI-generated code might use structuredClone, the dialog element, or CSS :has() selector without checking browser support. Test all interactive features — form submission, file upload, drag and drop — in every target browser.

Create a checklist of core user flows: landing page, signup, main feature, settings, and payment. Run through each flow in every target browser. Note visual differences, broken interactions, and console errors. Prioritize fixing issues that affect functionality over those that are purely cosmetic.

Automate what you can with tools like Playwright, which supports Chromium, Firefox, and WebKit (Safari's engine) out of the box. Even a small set of automated smoke tests run across three browser engines will catch most cross-browser regressions before your users do.