HTTP Status Codes

What every HTTP status code means, what typically causes it, and how to fix it — from 100 Continue through 508 Loop Detected, organized by the 1xx-5xx category.

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Why use HTTP Status Codes?

HTTP status codes are the three-digit numbers a server sends back with every response, and they follow a simple grouping: 1xx is informational, 2xx means success, 3xx means redirection, 4xx means the client did something the server couldn't process, and 5xx means the server itself failed. Knowing the category alone often tells you where to start looking — a 4xx means check your request, a 5xx means the problem is on the server's end. This reference covers every standard code with a plain-language explanation, the situations that typically produce it, and practical steps to resolve it — useful whether you're debugging an API integration, wondering what a browser error page means, or documenting your own API's responses.

Key benefits

Every standard status code covered, organized by category
Plain-language explanations, not just the RFC text
Practical causes and fixes for each code
Fast reference, no ads or clutter

Features

1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, 5xx Server Error
Common causes for each code
Fix guidance for both end users and site operators

Popular use cases

Looking up what a status code you saw in a browser or API response means
Debugging why an API integration is failing
Understanding a server error page (502, 503, 504)
Reference while building or documenting an API

How to use HTTP Status Codes

1
Find your code
Browse by category or jump directly to the code you're seeing.
2
Read what it means
Plain-language explanation of the status.
3
Check common causes and fixes
What typically triggers it and how to resolve it.

Frequently asked questions

What's the difference between a 4xx and 5xx error?

4xx codes indicate a client-side problem — something wrong with the request itself (bad syntax, missing auth, wrong URL). 5xx codes indicate a server-side problem — the request was fine, but the server failed to handle it correctly.

Why do I see different numbers for similar-sounding errors?

Status codes are deliberately specific — 401 (not authenticated) and 403 (authenticated but not authorized) look similar but mean different things, and choosing the right one helps API clients handle each case correctly.

Are there status codes not on this list?

This covers the standard codes defined by the HTTP specification (RFC 9110) plus a few common WebDAV extensions. Some services return non-standard codes for their own purposes, which won't appear here.

Last reviewed: September 2026

1xx Informational

2xx Success

3xx Redirection

4xx Client Error

5xx Server Error

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