# HTTP Status Codes List - Meaning of 200, 301, 404, 502 & More

> Complete HTTP status code reference: every 1xx–5xx code with its name and a plain-language explanation, searchable by code, name or keyword.

- URL: https://qilingtools.com/en/http-status
- Category: Developer Tools (https://qilingtools.com/en/dev)
- Tags: [Developer](https://qilingtools.com/en/tags/dev), [Network & HTTP](https://qilingtools.com/en/tags/network)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

When debugging an API, reading Nginx logs or troubleshooting a website, the status code is usually the first clue. This reference covers every standard HTTP status code defined by RFC 9110 and related specs (1xx informational, 2xx success, 3xx redirection, 4xx client errors, 5xx server errors), each with a plain-language explanation of when it appears and what usually causes it, including the differences between 301, 302, 307 and 308, between 401 and 403, and between 502 and 504. Type a code, name or keyword (like "cache" or "timeout") to filter; common codes are highlighted.

## How to use

1. Type a status code (e.g. 404 or 5), name or keyword in the search box
2. Or filter by class with the 1xx–5xx buttons
3. Read the name and detailed explanation of each code

## Features

- Every standard 1xx–5xx status code
- Plain-language explanation of usage and causes
- Grouped by class with class descriptions
- Search by code prefix, name or keyword
- Common and deprecated codes are marked
- Explains confusing pairs like 301/302/307/308, 401/403, 502/504
- Static reference, no network requests
- Free, no sign-up

## FAQ

### What is the difference between 301 and 302?

301 is a permanent redirect: search engines transfer ranking to the new URL and update their index. 302 is temporary and the original URL is kept. If a POST must stay a POST after redirecting, use 308 and 307 respectively.

### What is the difference between 401 and 403?

401 means you are not authenticated or authentication failed; logging in or sending a valid token fixes it. 403 means the server knows who you are but you lack permission, so logging in again will not help.

### What causes 502 vs 504?

Both come from a gateway or reverse proxy such as Nginx or a CDN. 502 Bad Gateway means the upstream returned an invalid response, often because the backend crashed or the port is wrong; 504 Gateway Timeout means the upstream took longer than the proxy was willing to wait.

### Do I need to sign up or pay?

No. The site is completely free, needs no account and has no usage limits.

## Related tools

- [JSON Formatter](https://qilingtools.com/en/json): Free online JSON formatter: beautify or minify, validate with the exact line and column of any error, browse a collapsible tree, sort keys and escape strings.
- [Base64 Encode/Decode](https://qilingtools.com/en/base64): Free online Base64 encoder and decoder: UTF-8 safe, optional URL-safe variant, convert text to Base64 and back in real time. Processed locally, never uploaded.
- [URL Encode/Decode](https://qilingtools.com/en/url-encode): Free online URL encoder and decoder with encodeURIComponent and encodeURI modes. Escapes Chinese, spaces and special characters. Real-time and local, no upload.
- [JWT Decoder](https://qilingtools.com/en/jwt): Free online JWT decoder: decode the header and payload of a JSON Web Token, show expiry and issued-at times, all locally without uploading the token.
- [Timestamp Converter](https://qilingtools.com/en/timestamp): Free online Unix timestamp converter: convert timestamps and dates, auto-detect seconds or milliseconds, and show local, UTC, ISO 8601 and relative time.
- [Hash / Checksum](https://qilingtools.com/en/hash): Free online hash calculator: SHA-1, SHA-256, SHA-384 and SHA-512 of text or any file through the browser crypto API. Files never leave your device.
- [UUID Generator](https://qilingtools.com/en/uuid): Free online UUID generator: create RFC 4122 UUID v4 in bulk with a cryptographic RNG. Options for uppercase, no hyphens and braces, with one-click copy.
- [Base Converter](https://qilingtools.com/en/base-convert): Free online number base converter: convert between binary, octal, decimal, hexadecimal and any base 2–36. Uses BigInt for huge integers, computed locally.