A 404 error appears when a server cannot find the requested resource at the specified URL. In WordPress, this problem often occurs after changing permalink settings, migrating a website, registering a custom post type, or modifying rewrite rules. Sometimes the homepage works correctly while individual posts, pages, or product URLs return 404 errors.
Understanding how WordPress generates URLs makes troubleshooting much easier.
Why Do WordPress Permalinks Stop Working?
WordPress uses rewrite rules to translate readable URLs into internal query variables. For example, a URL such as /about-us/ must be interpreted as a request for the corresponding page.
When rewrite rules become outdated or conflict with custom routing logic, WordPress may fail to resolve a valid URL. Server configuration, incorrect permalink settings, and conflicting plugins can cause similar symptoms.
Step 1: Refresh the Permalink Rules
The simplest solution is often to regenerate WordPress rewrite rules.
Log in to the administration dashboard and navigate to Settings → Permalinks. Review the existing structure and click Save Changes without necessarily changing anything.
WordPress will attempt to refresh its rewrite rules. Test several affected URLs afterward.
Avoid repeatedly saving permalinks as a permanent fix. If the problem returns, investigate what is modifying or breaking the rules.
Step 2: Check Server Rewrite Configuration
On Apache servers, WordPress commonly relies on .htaccess rules to route requests to index.php.
If the file is missing, corrupted, or not writable, pretty permalinks may fail. Check that Apache has the necessary rewrite module enabled and that the server allows the required overrides.
On Nginx, permalink routing is generally configured in the server configuration rather than through .htaccess.
Do not copy configuration snippets blindly. Existing security rules, custom routing, and hosting-specific settings may require adjustments.
Step 3: Investigate Custom Post Types
Custom post types introduce additional rewrite rules. A registration mistake can prevent their URLs from resolving correctly.
Review the register_post_type() configuration, particularly the rewrite, public, and query-related settings. If the post type uses a custom rewrite slug, check whether that slug conflicts with an existing page or another post type.
After changing the registration settings, flush rewrite rules during plugin activation or an appropriate administrative operation. Do not flush them on every page request because this can create unnecessary overhead.
Step 4: Look for URL Conflicts
A page and a custom post type may compete for the same URL pattern. Custom rewrite rules that match every single-segment URL can also intercept requests intended for ordinary pages.
Review custom rewrite_rules_array, request, parse_request, and post_type_link filters when the issue began after adding custom PHP code.
Test the affected URL alongside working pages to determine which routes are being intercepted.
Step 5: Clear Caches and Check Migration Settings
Clear relevant page caches, CDN caches, and browser caches after correcting the configuration. If the website was migrated, verify the WordPress Address and Site Address under Settings → General and check whether internal links still point to the old domain.
Final Thoughts
Start with the permalink settings, then examine server configuration, custom post types, and routing conflicts. If only specific URLs fail, focus on their rewrite patterns rather than changing the entire website configuration. Back up important files before modifying routing code.