4xx status codes are HTTP response codes that indicate a client side error, meaning the request could not be completed because of an issue with the URL or access permissions. The most common is 404 Not Found, which means the server cannot find the requested page. Another important one is 403 Forbidden, which means the server understood the request but is refusing to provide the content, often due to permissions or security rules.
In SEO, 4xx codes matter because they affect how search engines crawl your site and how users experience it. A small number of 404s is normal, especially when content is removed, but widespread 4xx errors can waste crawl budget, break internal links, and send visitors to dead ends. To keep information clear and reliable, fix broken links, update or remove outdated URLs from your sitemap, and use redirects only when there is a truly relevant replacement page. When a page is gone for good, returning the correct status code helps search engines understand the situation and prevents confusion.
