About

Every time a web browser requests a page, the server responds with a three-digit number known as an HTTP status code. These codes act as a communication shorthand, informing the client (browser) whether the request was successful, if a redirect is needed, or if an error occurred.

Understanding these codes is vital for web developers, SEO specialists, and system administrators. While a standard user might only recognize the infamous '404 Not Found', there are dozens of specific codes that help diagnose network health, manage link equity in SEO, and troubleshoot server-side applications efficiently.

Formulas

HTTP status codes are categorized into five distinct classes based on the first digit of the three-digit code. This structure allows the client software to determine the general type of response even if it does not recognize the specific code.

1xx (Informational): The request was received, continuing process.
2xx (Successful): The request was successfully received, understood, and accepted.
3xx (Redirection): Further action needs to be taken in order to complete the request.
4xx (Client Error): The request contains bad syntax or cannot be fulfilled.
5xx (Server Error): The server failed to fulfill an apparently valid request.

The system logic maps the integer input to a predefined dictionary of standard IETF protocols.

Reference Data

Code	Name	Category	SEO Impact
200	OK	Success	Positive (Standard)
301	Moved Permanently	Redirection	Transfers Link Equity
302	Found (Temporary)	Redirection	Does Not Transfer Equity
400	Bad Request	Client Error	Negative if persistent
401	Unauthorized	Client Error	Neutral (Requires Login)
403	Forbidden	Client Error	Negative (Access Denied)
404	Not Found	Client Error	Negative (Broken Link)
410	Gone	Client Error	Removes from Index
500	Internal Server Error	Server Error	Very Negative
503	Service Unavailable	Server Error	Temporary (Retry Later)

Frequently Asked Questions

A 301 redirect indicates a permanent move and passes 90-99% of link equity (ranking power) to the new URL. A 302 redirect indicates a temporary move and generally does not pass link equity, meaning search engines may keep the old URL indexed.

A 500 error is a generic 'catch-all' response indicating the server encountered an unexpected condition. Common causes include errors in the .htaccess file, syntax errors in server-side scripts (PHP, Python, etc.), or exhausted memory limits.

A few 404 errors are normal on the web. However, if high-authority external links point to a 404 page, you lose that 'link juice.' Additionally, a high volume of internal 404s provides a poor user experience, which can indirectly affect rankings.

A Soft 404 occurs when a server returns a 200 OK status code for a page that looks like an error page (e.g., 'Product out of stock' or 'Content not found'). This confuses search engines because they try to index a page that shouldn't exist.