Error map
.htaccess: Invalid command (500 Internal Server Error) Apache: [core:alert] /var/www/html/.htaccess: Invalid command 'php_value', perhaps misspelled or defined by a module not included in the server configuration
Nginx / Apache · layer 3, Edge & web server
Centre: this error. First ring: errors it is linked with (7). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (7)
Apache: AH00558: apache2: Could not reliably determine the server's fully qualified domain name
A harmless startup warning: Apache has no global ServerName, so it guessed one from the host’s IP.
Apache: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:80 / AH00015: Unable to open logs
Another process (Nginx, another Apache, Skype/IIS-like service) already listens on the port Apache wants.
Apache: AH00124: Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary
Rewrite rules loop internally, so Apache aborts with a 500.
Apache: AH00091: apache2: could not open error log file /var/log/apache2/error.log. AH00015: Unable to open logs (Permission denied)
Apache can't open its log files — permissions, a missing directory or disk problems.
Apache: AH00526: Syntax error on line 12 of /etc/apache2/sites-enabled/site.conf: Invalid command 'Foo', perhaps misspelled or defined by a module not included in the server configuration
Apache's config has a syntax problem or a directive from a module that isn't loaded.
Apache: [authz_core:error] AH01630: client denied by server configuration: /var/www/html/
Apache 2.4 authorisation denied access to the directory (403) because no `Require all granted` applies.
Apache: [core:error] AH00037: Symbolic link not allowed or link target not accessible: /var/www/html/current
Apache refuses to follow a symlink because `FollowSymLinks`/`SymLinksIfOwnerMatch` isn't allowed or the target isn't readable.
Two steps away (20)
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
OAuth Error: redirect_uri_mismatch
The redirect URI in your OAuth request doesn’t exactly match one registered for the client in the provider’s console.
WordPress: Error Establishing a Database Connection
WordPress can’t connect to its MySQL/MariaDB database with the credentials in wp-config.php, or the database server is down.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
Error: listen EACCES: permission denied 0.0.0.0:80
Node isn’t allowed to bind that port — ports below 1024 need root on Linux/macOS, and some Windows ports are reserved.
[nodemon] app crashed - waiting for file changes before starting...
Your app threw an error on startup; nodemon is waiting for a file change to retry.
WordPress: 404 Not Found on every page except the homepage (permalinks / .htaccess / Nginx rules)
Pretty permalinks aren’t being routed to index.php — .htaccess is missing/ignored (Apache) or Nginx lacks try_files.
Nginx: [error] rewrite or internal redirection cycle while internally redirecting to "/index.php" (500 Internal Server Error)
Nginx kept internally redirecting (more than 10 times), typically from a `try_files` or `rewrite` that points back to itself.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
HTTP 499 Client Closed Request (Nginx)
Nginx-specific code logged when the client disconnected before the server finished responding.
Apache: AH02240: Server should be SSL-aware but has no certificate configured / SSLCertificateFile: file '/etc/ssl/x.crt' does not exist or is empty
Apache cannot find the certificate or key file named in its configuration, or `SSLEngine on` is set without any certificate.
PHP Parse error: syntax error, unexpected …
PHP can’t parse the file because of a syntax mistake — the real error is often on the line before the one reported.
Apache: [ssl:warn] AH01909: example.com:443:0 server certificate does NOT include an ID which matches the server name
Apache's SSL virtual host name does not match any name inside the certificate it loads.
Nginx: nginx: [emerg] unexpected end of file, expecting ";" or "}" in /etc/nginx/conf.d/site.conf:42
The config ends while a block or directive is still open — a missing `}` or `;`.
HTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
Nginx: [error] directory index of "/var/www/html/" is forbidden (403 Forbidden)
A directory was requested but no index file exists (or index is wrong) and autoindex is off, so Nginx returns 403.
Apache: AH00112: Warning: DocumentRoot [/var/www/example.com/public_html] does not exist
A virtual host points to a directory that doesn't exist.
Too many levels of symbolic links (ELOOP)
A symlink points to itself, directly or through a chain, so path resolution loops.
Nginx: [error] open() "/home/user/site/index.html" failed (13: Permission denied), 403 Forbidden
The nginx worker user can't read the requested file or traverse a parent directory.
Apache: [core:info] AH00128: File does not exist: /var/www/html/favicon.ico (404)
The requested file isn't in the DocumentRoot — a normal 404 entry in the Apache error log.
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Popular: 500403400ORA-009331064Critical errorFileNotFoundException assemblyTypeError