A Comprehensive List Of All HTTP Status Codes

HTTP (Hypertext Transfer Protocol) codes are numerical status codes that indicate the status of a request made to a server.

In simple terms, when a client (such as a web browser) makes a request to a server, the server returns an HTTP code to inform the client of the request's result.

As an SEO, it's crucial for you to know what each HTTP code stands for.

While some HTTP codes like 3xx and 4xx codes are more necessary than others, it always helps if you know it all.

In this edition of the SEOBits Newsletter, I'll be exploring various HTTP codes and what each code means.

List Of Various HTTP Status Codes

1xx Status Codes

A 1xx response code is an informational type of status code that indicates that the initial request has been received and understood by the server.

The following list contains all the 1xx response codes supported by HTTP, along with brief descriptions for each:

100 Continue: The server has received the initial request and is continuing to process it.

101 Switching Protocols: The client requests a change in protocol from what was originally requested.

102 Processing: The server is processing the request but hasn't finished yet.

103 Early Hints: An indication that some resources may be ready to be sent before the complete response.

2xx Codes

A 2xx response code indicates that the request by the client has been successfully received, understood, and accepted by the server.

The following list contains all the 2xx response codes supported by HTTP, along with brief descriptions for each:

200 OK: A successful response indicating that the request was fulfilled.

201 Created: Indicates that a new resource has been created as a result of the request.

202 Accepted: The server has accepted the request, but it may not be acted upon yet.

203 Non-Authoritative Information: The information from this response comes from sources other than the origin server.?

204 No Content: Another successful status code indicating that no content is returned with this response.?

205 Reset Content: Indicates to user-agents to reset any forms or controls they have activated.?

206 Partial Content: An indication that only partial content is being sent in response to a range request by a client.?

207 Multi-Status: Contains multiple items in its body with separate responses for each item.

3xx Status Codes

A 3xx response code indicates that the client must take further action to complete its request.

300 Multiple Choices: Indicates that the requested resource can be accessed from multiple locations.?

301 Moved Permanently: Indicates that a resource has been moved to a new location, and future requests should use the new URI.?

302 Found: Temporarily redirects the client to another location while retaining the original request method.?

303 See Other: The server directs the user-agent to retrieve a different URI through GET instead of using POST.?

304 Not Modified: Indicates that an existing resource on the server matches the condition given in the If-Modified-Since header in the request.?

305 Use Proxy: This redirection code requires that requests be made through a proxy specified by the Location header field.?

307 Temporary Redirect: A more specific version of 302 Found, this code allows clients to access resources from alternative locations only for this request.

4xx Status Codes

A 4xx response code indicates an error in fulfilling a request that may be due to several reasons.

400 Bad Request: The server could not understand the request due to invalid syntax.?

401 Unauthorized: A user needs to authenticate in order to gain access to a resource.?

402 Payment Required: This response code is reserved for future use and does not currently have any functionality.?

403 Forbidden: Access to a requested resource is denied, and no other appropriate response is available.?

404 Not Found: Indicates that the requested resource cannot be found on the server.?

405 Method Not Allowed: The method specified in the request is not allowed for this resource.?

406 Not Acceptable: The resource identified by the request is only capable of producing content in formats not accepted by the Accept headers sent in the request.?

407 Proxy Authentication Required: Similar to 401 Unauthorized; however, it must be done through proxy authentication instead.

408 Request Timeout: The client did not produce a request within the time that the server was willing to wait.?

409 Conflict: A conflict between the current state of the resource and the requested operation has occurred.?

410 Gone: Indicates that the requested resource is no longer available at the server, and no forwarding address is known.?

411 Length Required: The server refuses to accept requests without an appropriate "Content-Length" header defined.?

412 Precondition Failed: One or more preconditions given in the request header fields are evaluated as false when tested on the server.?

413 Payload Too Large: Requests larger than what is allowed by the server will receive this response code.?

414 URI Too Long: The requested URL exceeds what is allowed by the server’s configuration.?

415 Unsupported Media Type: Indicates that the media type of a provided request body does not match with what is expected by the location for which it was sent.?

416 Range Not Satisfiable: When a range of bytes retrieved from a resource is unsatisfactory, this response code will be sent back to indicate an incomplete download/upload.?

417 Expectation Failed: Indicates that an expectation given in an Expect request-header field could not be fulfilled by the server.??

418 I'm a teapot: This response is intended for humorous purposes, and the server will indicate that it is unable to brew coffee because it is a teapot.?

421 Misdirected Request: The request was directed at a server that is not able to produce a response.?

422 Unprocessable Entity: A request was well-formed but was unable to be followed due to semantic errors.?

423 Locked: It indicates that the resource being accessed is locked and prevents the action from being completed.?

424 Failed Dependency: It indicates that a previous request failed in order for the current request to be successful.?

425 Too Early: It indicates that the server has received an early-hints header field in a request, but it cannot process it at this time.??

426 Upgrade Required: It indicates that the client must switch protocols in order to gain access to requested resources.?

428 Precondition Required: The client must provide certain conditions (such as authentication or payment) before it is allowed access to requested resources.

429 Too Many Requests: When requests are sent too frequently, then this response code will be sent back by the server as a way of preventing overloading.?

431 Request Header Fields Too Large: This response code indicates that one or more headers contained in the request were deemed too large by the server.

451 Unavailable For Legal Reasons: This code indicates that access to resources has been denied due to legal requirements, such as censorship laws or government restrictions.

5xx Status Codes

5xx Status codes indicate a server error.

500 Internal Server Error: It indicates that the server encountered an unexpected condition that prevented it from fulfilling the request.?

501 Not Implemented: When a server does not support the functionality needed to fulfill a valid request, then this response code will be sent back.?

502 Bad Gateway: This response code is sent when one server receives an invalid response from another server when attempting to fulfill the request.?

503 Service Unavailable: It indicates that the server is temporarily unable to process requests due to maintenance or overloading.?

504 Gateway Timeout: This indicates that a gateway or proxy did not receive a timely response from the upstream server.?

505 HTTP Version Not Supported: This Indicates that the version of HTTP used in the request is not supported by the server.???

506 Variant Also Negotiates: When content negotiation results in a circular reference, then this response code will be sent back by the server.??????

507 Insufficient Storage: This response code indicates that there was not enough storage space available in order to complete the request.??

508 Loop Detected: This occurs when a request contains an infinite loop and will cause additional requests until the memory limit is reached or a loop has been found.?

509 Bandwidth Limit Exceeded: It indicates that the user’s bandwidth limit has been exceeded and is no longer able to send any further requests.

510 Not Extended: This indicates that the server must not fulfill the request using the existing protocol but instead switch to an alternate one.?

511 Network Authentication Required: This response code indicates that access to the specified resource is only granted after successful authentication with a network-provided username and password.

Unofficial HTTP Status Codes

Unofficial HTTP request codes are response codes that are not part of the official HTTP specification.

They are usually used to provide additional information about an error or the status for a request.

420 Enhance Your Calm: This code indicates that the user has submitted too many requests in a short amount of time and should take a break before trying again.

450 Blocked By Windows Parental Controls: This code is sent when the server’s Windows Parental Controls have blocked access to the requested resource.

498 Invalid Token: This indicates that an expired or invalid token was sent with the request.

499 Token Required: This indicates that a valid token must be sent with any future requests in order to access any resources.

520 Unknown Error: Used when no other 5xx error code is suitable; this indicates an unknown server-side error has occurred.

Cloudflare Specific HTTP Status Codes

Cloudflare HTTP codes from 520 to 530 are response codes that indicate a server-side error has occurred.

These codes typically relate to the origin server being down or temporarily unavailable.

520 Unknown Error: Used when no other 5xx error code is suitable; this indicates an unknown server-side error has occurred.?

521 Web Server Is Down: Sent by Cloudflare when their gateway server is down, this response code serves as an indication that an issue with their services has caused the connection to fail.?

522 Connection Timed Out: This code indicates that the request was not completed within the specified time period and was canceled by the server due to a timeout.?

523 Origin Is Unreachable: Indicates that the origin server (the destination of the request) is currently unreachable.?

524 A Timeout Occurred: This code indicates that a timeout has occurred on one of Cloudflare’s edge servers while waiting for a response from the origin.?

525 SSL Handshake Failed: This code indicates an error occurred in establishing a secure (TLS/SSL) connection to the origin server.?

526 Invalid SSL Certificate: Indicates that the SSL certificate presented by the origin is invalid or expired.?

527 Railgun Error: This code indicates an error occurred with Cloudflare’s Railgun technology.

530 Origin DNS Error: This code is returned when Cloudflare cannot discover which hostname is associated with a given IP address.

These are the HTTP Status codes that come to my mind. Can you add more to the list?

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