Complete Guide to HTTP Status Codes (1xx, 2xx, 3xx, 4xx, 5xx) Explained
- April 08, 2010
When browsing the web, every request you make whether opening a page, submitting a form, or calling an API receives a response from the server. These responses come with HTTP status codes, which tell you exactly what happened behind the scenes.
Understanding HTTP status codes is essential for developers, SEO professionals, and website owners. In this guide, we’ll break down all major categories and explain what each code means in a simple, practical way.
What Are HTTP Status Codes?
HTTP status codes are 3-digit numbers returned by a server to indicate the result of a client’s request. They help identify whether a request was successful, failed, or needs further action.
Each status code belongs to one of five categories:
- 1xx - Informational
- 2xx - Success
- 3xx - Redirection
- 4xx - Client Errors
- 5xx - Server Errors
1xx - Informational Status Codes
These codes indicate that the request has been received and the process is continuing.
Common 1xx Codes:
- 100 Continue - The server has received the request headers, continue sending the body.
- 101 Switching Protocols - Server is switching protocols as requested.
- 102 Processing - The server is processing the request but no response yet.
These are rarely seen in everyday browsing but are important in backend communications.
2xx - Success Status Codes
These codes mean the request was successfully received, understood, and processed.
Common 2xx Codes:
- 200 OK - Request succeeded (most common).
- 201 Created - A new resource has been created.
- 202 Accepted - Request accepted but not yet processed.
- 203 Non-Authoritative Information - Response modified from original source.
- 204 No Content - Request successful, but no content returned.
- 205 Reset Content - Client should reset the document view.
- 206 Partial Content - Partial response (used in downloads/streaming).
- 207 Multi-Status - Multiple status responses (WebDAV).
If everything works fine on your website, you’ll mostly see 200 OK.
3xx - Redirection Status Codes
These codes indicate that further action is required to complete the request.
Common 3xx Codes:
- 300 Multiple Choices - Multiple response options available.
- 301 Moved Permanently - URL has permanently changed (important for SEO).
- 302 Found - Temporary redirect.
- 303 See Other - Redirect to another resource using GET.
- 304 Not Modified - Cached version is still valid.
- 305 Use Proxy - Must use a proxy to access the resource.
- 307 Temporary Redirect - Temporary redirect without method change.
Avoid redirect loops more than 5 redirects usually indicates a problem.
4xx - Client Error Status Codes
These errors occur when the issue is on the client side (browser/request).
Common 4xx Codes:
- 400 Bad Request - Invalid request syntax.
- 401 Unauthorized - Authentication required.
- 402 Payment Required - Reserved for future use.
- 403 Forbidden - Access denied.
- 404 Not Found - Resource not found (very common).
- 405 Method Not Allowed - HTTP method not supported.
- 406 Not Acceptable - Cannot generate acceptable response.
- 407 Proxy Authentication Required - Proxy authentication needed.
- 408 Request Timeout - Request took too long.
- 409 Conflict - Conflict with current state.
- 410 Gone - Resource permanently removed.
- 411 Length Required - Missing content length header.
- 412 Precondition Failed - Conditions not met.
- 413 Payload Too Large - Request too large.
- 414 URI Too Long - URL too long.
- 415 Unsupported Media Type - Invalid content type.
- 416 Range Not Satisfiable - Invalid range request.
- 417 Expectation Failed - Expectation not met.
- 422 Unprocessable Entity - Validation failed.
- 423 Locked - Resource is locked.
- 424 Failed Dependency - Dependency failure.
- 426 Upgrade Required - Protocol upgrade needed.
The most common issue developers debug is 404 Not Found.
5xx - Server Error Status Codes
These codes indicate that the server failed to fulfill a valid request.
Common 5xx Codes:
- 500 Internal Server Error - Generic server error.
- 501 Not Implemented - Functionality not supported.
- 502 Bad Gateway - Invalid response from upstream server.
- 503 Service Unavailable - Server overloaded or down.
- 504 Gateway Timeout - Upstream server timeout.
- 505 HTTP Version Not Supported - Unsupported HTTP version.
- 506 Variant Also Negotiates - Configuration error.
- 507 Insufficient Storage - Not enough storage space.
- 510 Not Extended - Further extensions required.
Frequent 5xx errors can negatively impact SEO and user experience.
Why HTTP Status Codes Matter for SEO
- 301 redirects help preserve link equity
- 404 errors hurt user experience
- 500 errors can reduce search engine trust
- 200 status ensures proper indexing
Keeping your status codes clean improves both ranking and performance.
Conclusion
HTTP status codes are more than just numbers they’re critical signals that help you understand how your website behaves.
Whether you're debugging an issue, optimizing SEO, or building APIs, knowing these codes will save you time and improve your workflow.
Frequently Asked Questions - FAQ
Joydeep Deb
Senior Digital Marketer & Project Manager
Joydeep Deb is a results-driven Senior Digital Marketer and Project Manager with deep expertise in Lead Generation and Online Brand Management. An IIM Calcutta Alumni with an MBA in Marketing, he specializes in SEO, SEM (PPC), and Web Technologies.
Based in Bangalore, Karnataka - India.