Why is it necessary to perform testing on different browsers?

Different browsers use different rendering engines for web pages (for example, Blink in Chrome, Quantum in Firefox, WebKit in Safari) and interpret HTML, CSS, and JavaScript in various ways. This can lead to the following issues:

• Display differences. Elements may look or be positioned differently depending on the browser.
• Compatibility problems. Some functions or APIs may behave differently or not work at all in certain browsers.
• Different performance. The loading and rendering speed of the page may vary.
• Plugins and extensions. User-installed plugins can affect the application's operation.
• Different browser versions. Even within the same browser, older versions may have compatibility issues with new technologies.

Therefore, cross-browser testing ensures that the web application functions correctly and provides a consistent user experience for the widest possible audience, regardless of the browser they use.