Handling 404 pages properly is essential for React applications to provide users with helpful feedback when they navigate to non-existent routes. As the creator of CoreUI, a widely used open-source UI library, I’ve implemented 404 handling in countless React applications and admin dashboards. From my 25 years of experience in web development and 11 years with React, the most effective approach is to use a catch-all route with the wildcard path * at the end of your route definitions. This pattern ensures all unmatched routes display a user-friendly not found page.