SEO and HTTP Status Codes: Everything You Need to Know!

What Are HTTP Status Codes?

HTTP status codes are three-digit numbers a server generates in response to a request from a client, such as a browser. These codes indicate whether the request was successful, redirected, or encountered an error. They are essential for understanding website behaviour and can significantly impact SEO and user experience.

Types of HTTP Status Codes

HTTP status codes are divided into five main categories:

• 1XX – Informational

Indicates that the request was received and the server is continuing the process.

• 2XX – Success

Confirms that the request was successfully received, understood, and accepted.

Example: 200 OK

• 3XX – Redirection

It shows that the requested resource has moved and additional steps are needed to complete the request.

Examples: 301 Moved Permanently, 302 Found

• 4XX – Client Errors

Indicates that the request cannot be fulfilled due to an issue on the client’s side, such as a missing page.

Examples: 404 Not Found, 403 Forbidden

• 5XX – Server Errors

Signals that the server failed to complete a valid request due to an internal problem.

Examples: 500 Internal Server Error, 503 Service Unavailable

Complete List of HTTP Status Codes

Code	Category	Name	Description
100	1XX – Informational	Continue	Server received the request headers; the client should proceed.
101	1XX – Informational	Switching Protocols	Server agrees to switch to a different protocol.
102	1XX – Informational	Processing (Deprecated)	The server is processing the request, but it has not yet completed.
103	1XX – Informational	Early Hints	The server sends headers before the final response is ready.
200	2XX – Success	OK	The request was successful; the response depended on the method used to make the request.
201	2XX – Success	Created	The request was successful, and a new resource was created.
202	2XX – Success	Accepted	Request accepted but not yet processed.
203	2XX – Success	Non-Authoritative Information	The response comes from a third-party source.
204	2XX – Success	No Content	Request successful, but no content returned.

Code	Category	Name	Description
205	2XX – Success	Reset Content	The request was successful; the client should reset the view.
206	2XX – Success	Partial Content	Only part of the resource was sent.
207	2XX – Success	Multi-Status	Contains multiple status codes for multiple operations.
208	2XX – Success	Already Reported	The resource has already been reported earlier.
226	2XX – Success	IM Used	Response includes delta updates (partial resource changes).
300	3XX – Redirection	Multiple Choices	Multiple responses are available; the user must select one.
301	3XX – Redirection	Moved Permanently	Resource permanently moved to a new URL.
302	3XX – Redirection	Found	Resource temporarily located at a different URL.
303	3XX – Redirection	See Other	The client should use a GET request at another URI.
304	3XX – Redirection	Not Modified	Resource not modified; use cached version.
305	3XX – Redirection	Use Proxy (Deprecated)	The client must use a proxy to access the resource.
307	3XX – Redirection	Temporary Redirect	Temporary redirection; the request method must not change.
308	3XX – Redirection	Permanent Redirect	Permanent redirection; the method must not change.
400	4XX – Client Error	Bad Request	The server cannot process the request due to a client-side error.
401	4XX – Client Error	Unauthorized	Authentication is required and has failed or not been provided.

Code	Category	Name	Description
402	4XX – Client Error	Payment Required	Reserved for future use; rarely used.
403	4XX – Client Error	Forbidden	The server understands the request but refuses to authorise it.
404	4XX – Client Error	Not Found	The requested resource is not available.
405	4XX – Client Error	Method Not Allowed	The HTTP method is not supported for the requested resource.
406	4XX – Client Error	Not Acceptable	The requested resource is not available in an acceptable format.
407	4XX – Client Error	Proxy Authentication Required	The client must authenticate with a proxy server.
408	4XX – Client Error	Request Timeout	The server timed out waiting for the request.
409	4XX – Client Error	Conflict	Request conflicts with the server’s current state.
410	4XX – Client Error	Gone	The requested resource has been permanently removed.
411	4XX – Client Error	Length Required	The Content-Length header is required.
412	4XX – Client Error	Precondition Failed	The preconditions given in the request were not met.
413	4XX – Client Error	Content Too Large	The request is larger than the server can process.
414	4XX – Client Error	URI Too Long	The requested URI is too long for the server to process.
415	4XX – Client Error	Unsupported Media Type	The media type in the request is not supported.

Code	Category	Status	Description
416	4XX – Client Error	Range Not Satisfiable	The requested range cannot be provided.
417	4XX – Client Error	Expectation Failed	The server cannot meet the requirements of the Expect header.
421	4XX – Client Error	Misdirected Request	The request was sent to the wrong server.
422	4XX – Client Error	Unprocessable Content	Request is well-formed but has semantic errors.
423	4XX – Client Error	Locked	The resource is currently locked.
424	4XX – Client Error	Failed Dependency	The request failed due to a previous request being failed.
425	4XX – Client Error	Too Early	The server is unwilling to risk processing a request that might be replayed.
426	4XX – Client Error	Upgrade Required	Client should switch to a different protocol.
428	4XX – Client Error	Precondition Required	Server requires request to be conditional.
429	4XX – Client Error	Too Many Requests	User has sent too many requests in a given amount of time.
431	4XX – Client Error	Request Header Fields Too Large	Headers are too large for the server to process.
451	4XX – Client Error	Unavailable for Legal Reasons	Resource is unavailable due to legal reasons.
500	5XX – Server Error	Internal Server Error	Server encountered an unexpected condition.
501	5XX – Server Error	Not Implemented	Server does not support the requested functionality.
502	5XX – Server Error	Bad Gateway	Server received an invalid response from the upstream server.
503	5XX – Server Error	Service Unavailable	Server is temporarily unable to handle the request.
504	5XX – Server Error	Gateway Timeout	Server did not receive a timely response from the upstream server.
505	5XX – Server Error	HTTP Version Not Supported	Server does not support the HTTP version used in the request.
506	5XX – Server Error	Variant Also Negotiates	Server encountered a configuration error.
507	5XX – Server Error	Insufficient Storage	Server is unable to store the representation needed to complete the request.
508	5XX – Server Error	Loop Detected	Server detected an infinite loop while processing the request.
510	5XX – Server Error	Not Extended	Request lacks necessary extensions.
511	5XX – Server Error	Network Authentication Required	Client must authenticate to gain network access.

How to Check a Webpage’s HTTP Status Code

HTTP status codes can be inspected directly through a browser’s developer tools. Here’s a simple method using Google Chrome:

• Navigate to the webpage in question.
• Right-click on the page and select “Inspect” or press Ctrl + Shift + I (Windows/Linux) or Cmd + Option + I (Mac) to open Developer Tools.
• Click the “Network” tab in the panel.
• Refresh the page using F5 or Ctrl + R.
• View the list of network requests. The “Status” column displays the HTTP status codes. The first request usually corresponds to the page’s HTML document.

Regular audits for HTTP status code errors are recommended to ensure optimal website performance and search engine accessibility.

SEO Implications of Common HTTP Status Codes

Understanding how different HTTP status codes affect SEO is essential for maintaining visibility in search engine results:

• 200 (OK):

Indicates successful page access. Pages returning this code are visible and indexable by search engines.

• 301 (Moved Permanently):

Indicates a permanent URL change. Search engines replace the old URL in their index with the new one, transferring ranking signals such as backlinks.

• 302 (Found / Temporary Redirect):

Signals a temporary change of URL. Search engines may continue indexing the original URL but may eventually treat it as permanent if left in place for an extended period.

• 404 (Not Found) / 410 (Gone):

These codes indicate the page no longer exists. A 410 provides a clearer signal to search engines that the content is gone permanently, potentially speeding up deindexing.

• 5XX (Server Errors):

Server-side issues that prevent a page from being loaded. Prolonged errors can impact crawling and indexing, affecting site visibility.

The Role of HTTP Status Codes in Large Language Models (LLMs)

HTTP status codes influence how large language models (LLMs) access and interpret web content. LLMs-powered tools, such as generative AI platforms, require successful responses to access and use content for indexing and training.

Error codes such as 404 or 500 prevent these tools from retrieving content. If persistent, these issues can lead to exclusion from AI-generated outputs, reducing a site’s exposure in modern discovery systems.

Experts emphasise the impact:

• Vincent Schmalbach, web developer and AI engineer, notes that pages returning 4XX and 5XX codes are often excluded from search engine results and AI-generated responses due to access failures.
• Toby Basalla, Principal Data Consultant at Synthelize, shares that misconfigured redirects can exclude critical pages from LLM training datasets, as seen in cases where temporary redirects were incorrectly applied to high-value landing pages.

Why Monitoring HTTP Status Codes Matters

Consistent monitoring of HTTP status codes across a website is essential for:

• Ensuring search engines can index all content.
• Preserving ranking signals during URL changes.
• Preventing crawl and indexing issues caused by server errors.
• Enabling AI-based tools to discover and use website content effectively.

Regular audits and quick resolution of errors improve site performance, stronger SEO results, and greater visibility across traditional search engines and AI platforms.