500 Internal Server Error

The server hit an unexpected condition that stopped it from fulfilling the request.

500 at a glance

Code: 500
Name: Internal Server Error
Class: 5xx Server error
Status: IANA-registered standard code
Defined in: RFC 9110, Section 15.6.1
Cacheable by default: No by default. Caches store it only when the response carries explicit freshness (Cache-Control max-age, s-maxage or Expires).

What 500 means

500 Internal Server Error is the catch-all for server-side failures. It tells the client nothing about the cause, by design: the details belong in the server logs, not in the response. Retrying may or may not help, depending on whether the fault is a bug or a transient problem.

What typically causes a 500

An uncaught exception in the application (Python traceback, Node.js unhandled error, Java exception, PHP fatal error).
Apache: a syntax error or unsupported directive in .htaccess (the error log says "Invalid command").
Misconfigured file permissions on CGI scripts, or a missing module/extension after an upgrade.
Database connection failures or exhausted pools surfacing as unhandled errors.
Running out of memory or disk while handling the request.

Fix it on the server

Check the application and web-server error logs at the timestamp of the request; the stack trace names the line.
Turn on error tracking (Sentry and similar) so every 500 is recorded with context.
Never show stack traces to users in production; return a generic page and a request ID they can quote.
If the failure is an upstream dependency, consider 502/503/504 instead so clients and monitors know what kind of failure it is.

Fix it as a client or visitor

Retry once after a short delay; if it persists, report it with the time and any request ID shown.
For APIs, check whether a specific input triggers it (a server bug on an edge case is common).

Headers that go with 500

Header	Role
`X-Request-Id`	Not standard, but many servers include a correlation ID to quote to support.

Example response

HTTP/1.1 500 Internal Server Error
Content-Type: application/json
X-Request-Id: 9f1c2e7a

{"error": "internal_error", "request_id": "9f1c2e7a"}