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HTTP Status Codes & Headers Inspector

Developer Utilities

Comprehensive HTTP status code reference and HTTP response header inspector. Search, filter, and inspect RFC 9110 / 9111 specifications for all 1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, and 5xx Server Error codes, along with copyable Express, Next.js, and Python code snippets.

100% Client-Side

404

Not Found

Specification: RFC 9110 §15.5.5
4xx ClassCacheable (Default)
RFC Definition & Meaning:

The origin server did not find a current representation for the target resource.

Developer Tip & Solution:

Verify URL endpoint route path, dynamic ID parameters, or database record existence.

Server Response Snippet:

Zero-Knowledge Privacy Guarantee

This HTTP Status Codes & Headers Inspector executes 100% locally in your browser’s JavaScript memory using client-side Web APIs. No inputs, keys, tokens, files, or outputs are ever uploaded to any server or logged in any database.

Key Features & Capabilities

  • Complete catalog of all 1xx, 2xx, 3xx, 4xx, and 5xx HTTP response codes
  • Instant real-time search by code number, name, or keyword
  • RFC 9110 & RFC 9111 caching and idempotency indicators
  • Ready-to-use backend snippets for Express.js, Next.js App Router, FastAPI, and Flask
  • Common HTTP Response Headers cheat sheet (Cache-Control, CORS, CSP, HSTS)

How to Use This Tool

  1. 1Search by status code number (e.g. 404, 502, 429) or name (e.g. Rate Limit, Timeout).
  2. 2Click on any status code to view its RFC description, caching behavior, and debugging tips.
  3. 3Copy backend code snippets for your preferred framework.

Frequently Asked Questions (FAQ)

401 Unauthorized means authentication is required (the user has not proved who they are), while 403 Forbidden means authentication was successful but the user does not have permission to access the resource.

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