500 Internal Server Error

Server error: the request may be fine, but the server failed to carry it out.

When a server should send it. When the server hit an unexpected condition and no more specific 5xx fits: an exception, a fatal error, a broken configuration. Log the details on the server and show the visitor a plain error page without stack traces.

Common causes. A bug or crash in the application, a PHP fatal error, a bad .htaccess rule, or a database error.

What to do. Visitors can only retry later. Site owners should check the server and application error logs, which name the actual failure.

Browsers and HTTP clients. Browsers show the body. Many HTTP clients retry 5xx for idempotent requests such as GET, but not for POST.

Google Search. Googlebot treats 5xx responses as a sign of trouble and temporarily slows its crawl rate. Already indexed URLs are kept at first, but are dropped if the errors continue. Source: Google Search Central, How HTTP status codes, and network and DNS errors affect Google Search.

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

HTTP/1.1 500 Internal Server Error
Content-Type: text/plain; charset=utf-8

Internal Server Error

location /example {
    return 500;
}

RewriteEngine On
RewriteRule ^example$ - [R=500,L]

http_response_code(500);
echo 'Internal Server Error';
exit;

res.writeHead(500, { 'Content-Type': 'text/plain' });
res.end('Internal Server Error');

# in a view function
return 'Internal Server Error', 500