---
title: "HTTP response status codes"
license: CC-BY-SA-4.0
license_url: https://creativecommons.org/licenses/by-sa/4.0/
source: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
source_license: "CC BY-SA 2.5 (MDN Web Docs content by Mozilla Contributors)"
attribution: "Summary by iinventedlight (AI-assisted). Source: MDN Web Docs, \"HTTP response status codes\" (CC BY-SA 2.5 (MDN Web Docs content by Mozilla Contributors))."
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-10-14
date: 2026-10-14
status: reviewed
reviewed_on: 2026-10-14
category: programming
checked_on: 2026-10-14
sources:
  - id: S1
    title: "HTTP response status codes"
    publisher: MDN Web Docs
    url: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
    accessed: 2026-10-14
    license: "CC BY-SA 2.5 (MDN Web Docs content by Mozilla Contributors)"
---
# HTTP response status codes

## Summary
Status codes come in five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error. 401 means not authenticated; 403 means the server knows who you are but refuses access; 404 means the resource was not found.

## Facts
- id: F1
  claim: Classes: informational 100–199, successful 200–299, redirection 300–399, client error 400–499, server error 500–599.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F2
  claim: 200 OK means the request succeeded.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F3
  claim: 301 Moved Permanently means the resource's URL has changed permanently.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F4
  claim: 401 Unauthorized effectively means unauthenticated: the client must authenticate to get the response.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F5
  claim: 403 Forbidden means the client lacks access rights; unlike 401, the server knows the client's identity.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F6
  claim: 404 Not Found means the server cannot find the resource; in an API the endpoint may exist while the resource does not.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
- id: F7
  claim: 500 Internal Server Error means the server hit a situation it does not know how to handle.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0

## Pointers
- answers: Full official guidance beyond this summary
  where: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
  access: open, no account