The react-app-polyfill package ensures compatibility of React applications with older browsers, particularly Internet Explorer 9, 10, and 11. It includes necessary polyfills for modern JavaScript features like fetch, Promise, and ES modules, allowing your application to function correctly in these environments. By incorporating this package, you can widen your application's reach and prevent common JavaScript errors in older browsers without significant code modifications. It's often used alongside Create React App projects to guarantee broader browser support.
