The Most Common 15 to 20 HTTP Status Codes you should know.

HTTP status codes are essential server responses that indicate whether a web request succeeded, failed, or requires further action. Understanding these codes helps users, developers, and website owners diagnose and fix issues efficiently.

In this guide, we’ll break down 20 critical HTTP status codes, categorized by their response classes (1xx to 5xx). For each, we’ll explain its meaning, common causes, and how to resolve it.

1. Informational Responses (1xx)

These codes indicate that the server has received the request and is processing it.

🔹 100 Continue

• Meaning: The server acknowledges the request and is ready for the client to proceed.

• When it occurs: Used in large file uploads or API requests where headers are sent first.

• Fix: Typically handled automatically; no user action needed.

🔹 102 Processing

• Meaning: The server is still handling a long-running request (e.g., complex API operations).

• When it occurs: Rare, mostly in applications with heavy backend processing.

• Fix: Wait for the server to complete the task.

2. Success Codes (2xx)

These indicate that the request was successfully processed.

🔹 200 OK

• Meaning: The request succeeded (e.g., webpage loaded correctly).

• Common use: Standard response for successful HTTP requests.

🔹 201 Created

• Meaning: A new resource (e.g., database entry) was successfully created.

• Example: After submitting a form or signing up for an account.

🔹 202 Accepted

• Meaning: The request was accepted but not yet processed.

• Example: Used in asynchronous operations where processing takes time.

🔹 204 No Content

• Meaning: The request succeeded, but there’s no content to return.

• Example: API calls that process data without returning a response body.

3. Redirection Codes (3xx)

These tell the client to take additional action to complete the request.

🔹 301 Moved Permanently

• Meaning: The resource has permanently moved to a new URL.

• SEO Impact: Essential for maintaining search rankings—always redirect properly.

🔹 302 Found (Temporary Redirect)

• Meaning: The resource is temporarily available at a different URL.

• Example: Used in A/B testing or short-term promotions.

🔹 304 Not Modified

• Meaning: The browser can use a cached version (no re-download needed).

• Fix: Hard refresh (Ctrl+F5) to fetch a fresh copy.

🔹 307 Temporary Redirect

• Meaning: Similar to 302, but guarantees the HTTP method won’t change.

• Use Case: Important for POST request redirects.

🔹 308 Permanent Redirect

• Meaning: Like 301, but ensures the HTTP method remains the same.

• Use Case: Critical for API and form submission redirects.

4. Client Errors (4xx)

These occur when the client makes an invalid or unauthorized request.

🔹 400 Bad Request

• Meaning: The server can’t process the request due to malformed syntax.

• Fix: Check for typos in URLs or API parameters.

🔹 401 Unauthorized

• Meaning: Authentication failed (missing or invalid credentials).

• Example: Incorrect login details.

🔹 403 Forbidden

• Meaning: The server refuses access (even if authenticated).

• Causes: Missing permissions, IP blocking, or .htaccess misconfigurations.

🔹 404 Not Found

• Meaning: The requested resource doesn’t exist.

• Fix: Restore deleted pages or fix broken links.

🔹 405 Method Not Allowed

• Meaning: The HTTP method (e.g., POST, GET) isn’t supported for the URL.

• Example: Sending a POST request to a read-only endpoint.

🔹 408 Request Timeout

• Meaning: The server timed out waiting for the request.

• Fix: Refresh or check your internet connection.

🔹 429 Too Many Requests

• Meaning: Rate limit exceeded (too many requests in a short time).

• Example: API abuse or DDoS protection triggers.

5. Server Errors (5xx)

These indicate the server failed to fulfill a valid request.

🔹 500 Internal Server Error

• Meaning: A generic server failure with no specific details.

• Fix: Check server logs or restart services.

🔹 502 Bad Gateway

• Meaning: A proxy server received an invalid response from the backend.

• Common causes: Nginx/Cloudflare misconfigurations.

🔹 503 Service Unavailable

• Meaning: The server is temporarily down (overloaded or in maintenance).

• Fix: Wait or contact the website admin.

🔹 504 Gateway Timeout

• Meaning: The proxy didn’t get a timely response from the backend.

• Fix: Increase timeout settings or optimize slow queries.

🔹 511 Network Authentication Required

• Meaning: The client must authenticate to access the network (e.g., public Wi-Fi login pages).

• Example: Captive portals in airports or hotels.

Final Thoughts

HTTP status codes help diagnose issues quickly:

• Users: Identify if the problem is client-side (4xx) or server-side (5xx).

• Developers: Debug API responses and server errors.

• SEO Specialists: Ensure proper redirects (301 vs. 302) for rankings.

Bookmark this guide for quick reference! Did we miss any important codes? Let us know !