What is the fundamental difference between a 'hard 404' and a 'soft 404' error, and how should each be addressed?

The fundamental difference between a 'hard 404' and a 'soft 404' error lies in the server's response and how search engines interpret it. A 'hard 404' error occurs when a web server correctly returns a 404 HTTP status code, indicating that the requested resource (page or file) is not found. This is the proper way to signal that a page doesn't exist. A 'soft 404' error, on the other hand, occurs when a server returns a 200 OK HTTP status code (meaning the request was successful) for a page that actually doesn't exist or contains very little content, effectively telling search engines that the page is valid when it's not. For example, a page displaying a 'Page Not Found' message but returning a 200 status code is a soft 404. Hard 404s should be addressed by ensuring that broken links are updated or removed, and by implementing custom 404 pages that guide users back to relevant content. Soft 404s are more problematic because search engines might index these pages as if they were valid, diluting the site's overall quality. Soft 404s should be fixed by either restoring the missing content, redirecting the URL to a relevant existing page (301 redirect), or by returning the correct 404 HTTP status code.