# HTTP status semantics

Canonical HTML: /atlas/http-status
Atlas version: atlas-2026-07-28-v1
Category: HTTP behavior and efficiency

## Definition

HTTP status codes tell a crawler whether a request succeeded, moved, failed temporarily, or failed permanently.

## How it works

A 200 offers a representation, 3xx redirects, 404 and 410 indicate absence, 429 asks for slower traffic, and 5xx signals a server-side failure.

## How to validate it

Store every hop with status, timestamp, latency, and retry context rather than collapsing a chain into the final body.

## Common failure

Returning a friendly error page with status 200 creates a soft 404 and makes failure look like valid content.

## Related topics

- [Redirect chains](/atlas/redirects)
- [retry-after](/atlas/retry-after)