What Are HTTP Status Codes?
HTTP status codes are three-digit numbers returned by a web server in response to a client's request. They communicate whether a request succeeded, failed, or requires further action.
Status codes are grouped into five categories: 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error). Each category serves a distinct purpose in the HTTP protocol.
Understanding these codes is essential for web developers, DevOps engineers, and SEO professionals. A 301 redirect passes link equity for SEO, a 429 signals rate limiting, and a 503 tells search engines to retry later. This tool helps you quickly look up any code and understand its meaning in context.
How to Use
- 1Browse all status codes or use the category tabs to filter by 1xx, 2xx, 3xx, 4xx, or 5xx.
- 2Type a code number, name, or keyword in the search box for instant filtering.
- 3Click any status code card to expand and see common use cases.
- 4Use the category descriptions to understand what each group represents.
- 5Reference this page anytime you encounter an unfamiliar HTTP response code.
When You Need This
Debugging API responses
When your API returns an unexpected status code, look it up here to understand what the server is communicating and how to handle it in your client code.
Configuring redirects for SEO
Choose between 301 (permanent) and 302 (temporary) redirects based on whether you want search engines to transfer page authority to the new URL.
Implementing error handling
Decide which HTTP status codes your API should return for different error conditions — 400 for bad input, 401 for missing auth, 403 for forbidden access, 422 for validation failures.
Reading server logs
When monitoring access logs or error logs, quickly decode status codes to identify patterns like bot rate-limiting (429) or broken internal routes (500).
Tips
Use specific codes over generic ones
Return 404 for missing resources, 409 for conflicts, and 422 for validation errors instead of overusing 400 Bad Request for everything.
Include helpful error bodies
The status code tells the category of the problem; the response body should explain the specific issue and how to fix it.
Respect the semantics for SEO
Use 301 for permanent moves, 410 for intentionally removed content, and 503 with a Retry-After header during maintenance.
Handle 429 with exponential backoff
When you receive rate-limit responses, back off exponentially rather than retrying immediately to avoid being blocked.
Examples
Successful API response
A GET request that returns data normally.
Input
GET /api/users/123Output
200 OK — The request succeeded and the server returned the user data.Resource not found
Requesting a page that does not exist.
Input
GET /api/users/99999Output
404 Not Found — The server cannot find the requested resource.Rate limited
Too many requests in a short time window.
Input
GET /api/search (100th request in 1 minute)Output
429 Too Many Requests — Wait and retry with exponential backoff.Limitations
- This reference covers standard HTTP/1.1 and common extension codes. Proprietary or application-specific codes (e.g., Cloudflare 520-527) are not included.
- Status code semantics can vary between implementations — some APIs use codes unconventionally.
- This tool is a reference lookup and cannot diagnose why your specific server returns a particular code.
Features
- Complete reference of 50+ standard HTTP status codes
- Instant search by code number, name, or description keyword
- Category filtering: Informational, Success, Redirection, Client Error, Server Error
- Expandable cards showing real-world use cases for each code
- Color-coded categories for quick visual identification
- SEO-relevant codes highlighted with redirect and crawl implications
- 100% client-side — no data uploaded, works offline once loaded
FAQ
What is the difference between 401 and 403?
401 Unauthorized means the request lacks valid authentication credentials — the client should authenticate and retry. 403 Forbidden means the server understood the request but refuses to authorize it, even with valid credentials. Authentication won't help with 403.
Should I use 301 or 302 for redirects?
Use 301 Moved Permanently when the URL has changed forever and you want search engines to transfer SEO value. Use 302 Found for temporary redirects where the original URL should remain canonical.
What does 418 I'm a Teapot mean?
It's a real HTTP status code from RFC 2324 (Hyper Text Coffee Pot Control Protocol), originally an April Fools' joke. Some APIs use it as an easter egg or to indicate the server intentionally won't process certain requests.
When should I return 422 vs 400?
400 Bad Request is for malformed requests (invalid JSON syntax, missing headers). 422 Unprocessable Entity is for well-formed requests with semantically invalid content (valid JSON but a field value fails validation).
How do status codes affect SEO?
301 passes ~95% of link equity to the new URL. 404 pages are eventually dropped from the index. 503 with Retry-After tells crawlers to come back later without penalty. 410 tells search engines the content is intentionally gone.
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Your Privacy
This is a pure reference tool. No data is sent to any server. All search and filtering happens entirely in your browser.
Tips & Related Workflows
- Need to encode special characters in URL parameters?URL Encoder.
- Format API response bodies for debugging?JSON Formatter.
- Test regex patterns for log parsing?Regex Tester.