500 Internal Server Error

Unexpected server-side failures preventing request completion produce the 500 Internal Server Error status code, a catch-all for conditions not covered by more specific server errors.

Table of Contents

Usage

The 500 Internal Server Error status code signals a generic failure on the server side. Due to the broad nature of this error, the specific cause depends on the environment. The web server is experiencing problems and the server administrator needs to take action to resolve the issue.

The error is often attributed to a permissions problem on one or more files, a script timeout, or corruption in the .htaccess file. The only certainty is the HTTP request was not fulfilled.

Example

The client requests a resource and the server responds with a 500 Internal Server Error status code, indicating the request will not be satisfied.

Request

GET /news.html HTTP/1.1
Host: www.example.re

Response

HTTP/1.1 500 Internal Server Error
Content-Type: text/html; charset=UTF-8
Content-Length: 139

<html>
  <head>
    <title>Request Failed</title>
  </head>
  <body>
    <p>The request failed due to a server error.</p>
  </body>
</html>

500 vs 502, 503, and 504

The four common 5xx codes point at different layers, which narrows the first diagnostic step.

Code What failed First place to look
500 The application itself raised an unhandled error Application logs and stack traces
502 A gateway got an invalid response from upstream Whether the upstream process is running
503 The server is up but declining requests Overload, maintenance mode, or a full worker pool
504 A gateway timed out waiting for upstream Slow queries or an unresponsive upstream

A 500 is not heuristically cacheable, so a CDN holds it only when the response carries explicit freshness. During an incident a 500 usually reaches every client rather than being served from cache.

How to fix

Start with the error log. In nginx, check /var/log/nginx/error.log. In Apache, check /var/log/apache2/error.log or /var/log/httpd/error_log. The log entry almost always names the failing file and line number.

Common root causes and their fixes:

  • File permissions. The web server process needs read access to application files and write access to upload or cache directories. On Linux, set directories to 755 and files to 644. Confirm the owner matches the web server user (www-data on Debian/Ubuntu, nginx or apache on RHEL/CentOS).
  • Corrupted .htaccess. On Apache, rename .htaccess temporarily to confirm. A single invalid directive or a reference to an unloaded module triggers a 500 for every request in the directory tree.
  • PHP fatal errors. Syntax errors, undefined function calls, and exceeded memory_limit all produce a 500. Set display_errors = Off and log_errors = On in php.ini, then read /var/log/php/errors.log. Raise memory_limit when the log shows "Allowed memory size exhausted."
  • PHP-FPM crashes. When nginx proxies to PHP-FPM and the pool dies, the error log shows "upstream prematurely closed connection." Check the PHP-FPM pool log for segfaults or out-of-memory kills. Increase pm.max_children if the pool runs out of workers.
  • Database connectivity. Wrong credentials, unreachable host, or connection pool exhaustion all surface as a 500. Test connectivity directly from the server (mysql -u user -p -h host or psql -U user -h host) to isolate the database from the application.
  • Disk full. A server with no free disk space fails to write temporary files, sessions, or logs. Run df -h and clear old logs, cache files, or core dumps.

After identifying the cause, deploy the fix and monitor the error log for recurrence. Set up log alerting to catch 500 spikes before users report them.

Code references

.NET

HttpStatusCode.InternalServerError

Rust

http::StatusCode::INTERNAL_SERVER_ERROR

Rails

:internal_server_error

Go

http.StatusInternalServerError

Symfony

Response::HTTP_INTERNAL_SERVER_ERROR

Python3.5+

http.HTTPStatus.INTERNAL_SERVER_ERROR

Java

java.net.HttpURLConnection.HTTP_INTERNAL_ERROR

Apache HttpComponents Core

org.apache.hc.core5.http.HttpStatus.SC_SERVER_ERROR
org.apache.hc.core5.http.HttpStatus.SC_INTERNAL_SERVER_ERROR

Angular

@angular/common/http/HttpStatusCode.InternalServerError

See also

Last updated: August 18, 2026