Every website is comprised of n number of technologies that are USED in the backend and frontend. Three major technologies used for the front end and in the rendering are HTML5, CSS3, and JavaScript.

Every browser has a different rendering engine to compute these three technologies. Chrome uses Blink, Firefox uses GECKO and IE uses edge HTML and Charka. Because of these rendering engines, the same website renders complete differently in all these different browsers and that is the reason why you need cross-browser testing. To ensure the website works fine and functions the same across different browser versions and on different operating systems, cross-browser testing is required.

Reasons for why cross-browser testing is required are -

1. To ensure browser COMPATIBILITY with different operating systems.
2. To ensure image orientation on different browsers.
3. Different orientation of Javascript on each browser can cause an issue.
4. To check font size mismatch or font not rendered properly.
5. To check compatibility with the new web framework.