HTTP status codes are standardized response codes issued by web servers to indicate the outcome of a client’s request. These three-digit codes are grouped into five classes, each serving a distinct purpose in web communications. Understanding these codes is essential for developers, SEO professionals, and website owners to diagnose issues and optimize web performance.
What Are HTTP Status Codes?
HTTP status codes are numeric responses that web servers send back to browsers or clients after receiving an HTTP request. Each code communicates specific information about the request’s outcome:
- Was the request successful?
- Does the resource need to be redirected?
- Is there a client or server error?
- What specific action should the browser take next?
The Five Classes of HTTP Status Codes
HTTP status codes are organized into five distinct categories, each serving a specific purpose in web communications:
1XX: Informational Responses
These codes indicate that the server has received the request and is continuing the process. They’re relatively uncommon in everyday browsing but play important roles in complex web applications.
Key examples include:
- 100 Continue: The server has received the request headers and the client should proceed to send the request body.
- 101 Switching Protocols: The server is switching protocols as requested by the client.
Read more on 1xx Status Codes Guide.
2XX: Successful Responses
These codes confirm that the client’s request was successfully received, understood, and accepted by the server.
Notable examples include:
- 200 OK: The standard response for successful HTTP requests
- 201 Created: The request has been fulfilled, resulting in the creation of a new resource
- 204 No Content: The server successfully processed the request but isn’t returning any content
Read more on 2xx Status Codes Guide.
3XX: Redirection Messages
These codes indicate that further action needs to be taken by the client to complete the request, typically involving a redirect to another URL.
Important examples include:
- 301 Moved Permanently (Most common 3xx error): The requested resource has been permanently moved to a new URL.
- 302 Found: The requested resource temporarily resides under a different URL
- 304 Not Modified: The resource hasn’t been modified since the last request
Read more on 3xx Status Codes Guide.
4XX: Client Error Responses
These codes indicate that the client appears to have made an error, such as requesting a non-existent page or lacking proper authentication.
Common examples include:
- 400 Bad Request: The server couldn’t understand the request due to invalid syntax.
- 403 Forbidden: The client doesn’t have permission to access the requested content.
- 404 Not Found: The server can’t find the requested resource.
Read more on 4xx Status Codes Guide.
5XX: Server Error Responses
These codes indicate that the server failed to fulfill a valid request due to an error with the server itself.
Key examples include:
- 500 Internal Server Error: A generic error message when the server encounters an unexpected condition
- 502 Bad Gateway: The server received an invalid response from an upstream server
- 503 Service Unavailable: The server is temporarily unable to handle the request
Read more on 5xx Status Codes Guide.
Why HTTP Status Codes Matter
For SEO Professionals
- Crawlability: Ensuring search engines can properly access and index content
- Redirect Management: Implementing proper redirects for moved content
- Error Handling: Addressing 4XX and 5XX errors that could negatively impact rankings
All this can and often results in loss of rankings of the affect pages and overall SEO performance.
For Website Owners
- User Experience: Preventing frustrating encounters with error pages
- Conversion Optimization: Ensuring customers can complete transactions without technical barriers
- Site Health Monitoring: Identifying potential issues before they impact business
Common HTTP Status Code Issues and Solutions
Redirect Problems
- Redirect Chains: Multiple consecutive redirects that slow down page loading
- Redirect Loops: Circular redirects that never reach a final destination
- Mixed Content Redirects: HTTP to HTTPS redirect issues
Client-Side Errors
- Broken Links: Links pointing to 404 pages
- Access Issues: Authentication and authorization problems resulting in 401 or 403 errors
- Invalid Requests: Malformed URLs or parameters causing 400 errors
Server-Side Challenges
- Server Overload: Handling 503 errors during traffic spikes
- Configuration Issues: Addressing 500 errors stemming from server misconfigurations
- Timeout Problems: Managing 504 Gateway Timeout errors
Monitoring HTTP Status Codes
Keeping track of HTTP status codes across your website is essential for maintaining optimal performance and user experience:
- Regular Website Audits: Use crawling tools such as Screaming Frog to identify status code issues
- Log File Analysis: Review server logs to catch errors users might not report
- Real-Time Monitoring: Set up alerts for critical error responses
- Search Console Integration: Monitor how Google experiences your site’s HTTP status codes
