The HTTP codes are the great unknown and now used for a variety of tasks such as SEO audits. Usually, the codes are formed by a number and a phrase that defines the error that the HTTP server is giving.
These HTTP codes can be of different types, all codes are specified in RFC documents, so they are standardised.
There are totally 5 types of HTTP codes. They are:
- 1XX codes – Informational Responses.
- 2XX codes – Requests correct.
- 3XX codes – Redirects.
- 4XX codes – Client Errors.
- 5XX codes – Server Errors.
As you can see, these code groups offer both confirmation information and error information that may occur, both on the client and on the server.
In this article we are going to show the HTTP codes that affect web environments, that is to say, the codes that only affect WebDAV like code 507 or code 508.
1XX CODES – Informational Responses
The codes 1XX are informative answers for the web browser, in real the user does not get to see these codes on his screen since they are usually messages or intermediate codes.
- CODE 100 – CONTINUE
This message means that the browser can perform the request, it is usually used to notify that the first part of the request has successfully arrived at the visitor’s browser.
- CODE 101 – SWITCHING PROTOCOLS
This message is used in the protocol changes that are proposed by the visitor’s browser, an example would be when negotiating the change from HTTP1.0 to HTTP1.1.
- CODE 102 – PROCESSING
This message is used when the server is still processing the request but is not yet finished. This is used so that the visitor’s browser does not think that the request has been lost.
- CODE 103 – CHECKPOINT
It is a message that is used when a POST or PUT request is to be resumed that was previously lost or aborted for some reason.
2XX CODES – Correct Requests
2XX Codes are simple confirmation messages that everything goes correctly and that it has been received, processed and responded correctly.
Ideally, all pages of a website respond with a code 200 OK or if we have redirected with a redirection 301 or similar.
CODE 200 – OK
This is the message that is used when the request has completed successfully, this is the main message to say that everything is fine.
- CODE 201 – CREATED
This messaged is used when the request has been created successfully and because of this a new resource has been created in a new URL, in addition, the confirmation message included the new URL created.
- CODE 202 – ACCEPTED
This code is answered by the server when it has successfully received the request but has not yet finished processing because it is a very complex request.
- CODE 203 – NON-AUTHORITATIVE INFORMATION
This code is answered when the request has been completed successfully, but the content obtained was not obtained directly from the server to which the request was made, but from another server.
- CODE 204 – NO CONTENT
This message is used when the request was successful, but the response does not contain any content.
- CODE 205 – RESET CONTENT
This message is used when the request has completed successfully, but the response has no content and the browser must reload the content of the page it was on.
- CODE 206 – PARTIAL CONTENT
This code is used when the request is completed successfully but only responds with part of the contents.
- CODE 207 – MULTI-STATUS
The response coming from this code is an XML file containing several different HTTP responses or codes, the number of responses depends on the request or previous requests made by the visitor’s browser.
3XX CODES – REDIRECTS AND ACTIONS
These codes or 3XX messages are used when in the browser you have to perform some added action such as a redirection.
- CODE 300 – MULTIPLE CHOICES
This code indicates that there are several options to access the same resource, it is used to indicate a request that calls more than one file for example.
- CODE 301 – MOVED PERMANENTLY
This code is used in redirects 301, used when the requested resource is not in that location but redirects to another side automatically.
301 redirects are very important for SEO, to avoid 404 errors.
- CODE 302 – MOVED TEMPORARILY
This code is used when the resource has been moved to another location and therefore a redirection is made to access the resource, but this redirection will only be active for a while, ie it is temporary.
- CODE 303 – SEE OTHER
This code is not usually used too much, it simply notifies the browser that the resource has been moved to a new URL, but the redirection is not done directly, although it does notify the new URL.
- CODE 304 – NOT MODIFIED
If the web browser asks if a resource has been modified since the last visit, the server responds with a 304 code if the requested resource has not changed since the last visit.
The 304 codes are beginning to be used for SEO, specifically to take advantage of the crawl budget assigned by Google.
- CODE 305 – USE PROXY
This code is used when the resource requested by the visitor’s browser has to be served from a proxy specified in the “Location” header.
- CODE 306 – PROXY SWITCH
Code 306 is deprecated but has not been deleted because it is reserved for use in future cases.
- CODE 307 – TEMPORARY REDIRECT
It is similar to redirection 301, but in this case, a temporary redirection is performed that will be valid at least in this request made but may not in future requests.
- CODE 308 – PERMANENT REDIRECT
Code 308 is similar to redirection 301 but does not allow changing the HTTP method for the new request (it is rarely used, except in exceptional cases).
4XX CODES – CLIENT ERRORS
4XX errors identify and report the errors where the web browser is responsible, and are solvable in different ways.
The best known 4XX error is error 404 which indicates that what is searched is not found, and in most cases is solved by a 301 redirect.
- CODE 400 – BAD REQUEST
4XX errors identify and report errors where the responsible is the web browser, are solvable in different ways.
The best-known 4XX error is error 404 which indicates that what is searched is not found, and in most cases is solved by a 301 redirect.
- CODE 400 – BAD REQUEST
This error code is used when the server is not able to understand the request of the visitor’s web browser and therefore the response …
- CODE 401 – UNAUTHORIZED
This error code is used when the page to which you want to access the browser needs authentication.
A “WWW-Authenticate” header is included for the browser to initiate the authentication process.
- CODE 402 – PAYMENT REQUIRED
This HTTP code is not yet used but is reserved and implemented for future use.
- CODE 403 – FORBIDDEN
This error code is used when, even though the request is successful, access to the requested resource is denied.
- CODE 404 – NOT FOUND
It is the typical 404 error that appears when something is not found, in particular, the code specifies that what was requested is not found and that it is also not possible to determine if the absence is temporary or permanent.
- CODE 405 – METHOD NOT ALLOWED
This code is returned when the browser uses a method not allowed by the server to obtain the resource requested by the browser.
- 406 CODE – NOT ACCEPTABLE
This message is returned when the requested resource is in a format that is not accepted by the browser.
- CODE 407 – AUTHENTIFICATION REQUIRED PROXY
This error code is similar to the 401 code, but this time the authentication must be done first in a proxy.
- CODE 408 – REQUEST TIMEOUT
This code appears when the browser has taken too long to send a request and the server is no longer waiting for its response, even so, the browser can send another request (from the beginning) anytime.
- CODE 409 – CONFLICT
This error occurs when the request could not be completed because a conflict has occurred, for example, when a PUT request attempts to modify a resource that has already been modified on the other hand.
- CODE 410 – GONE
This error code is similar to error 404, but in this case, specifies that the absence is permanent and that the resource being searched will never be available again.
- CODE 411 – LENGTH REQUIRED
This code is returned when the server rejects the browser request because it does not include the appropriate “Content-Length” header.
- CODE 412 – PRECONDITION FAILED
This code is returned when the server is unable to meet the conditions specified by the server.
- CODE 413 – REQUEST ENTITY TOO LARGE
Code 413 indicates that the request sent by the browser is very large and the server is not able to process it.
- CODE 414 – REQUEST-URI TOO LONG
This code appears when the URL of the request is too long to be processed, this usually happens when there are many parameters in the URL and in cases where a request is sent by GET and should be sent by POST so that the URL is shorter.
- CODE 415 – UNSUPPORTED MEDIA TYPE
This error message appears when the browser’s request to the server has a format that the server is unable to understand, so it can not be processed.
- CODE 416 – REQUESTED RANGE NOT SATISFIABLE
This error code usually appears when the browser downloads a very large file in parts and incorrectly calculates the size of one of the parts.
- CODE 417 – EXPECTATION FAILED
This error appears when it is impossible to process the request because it does not meet the requirements of the “Expect” header.
- CODE 418 – I’MA TEAPOT
This is a code implemented as a joke, not used for anything useful.
- CODE 422 – UNPROCESSABLE ENTITY
This code means that the browser request has the correct format, but the contents have some type of error that prevents the server from being able to respond correctly.
- CODE 423 – LOCKED
This error code appears when the resource requested by the visitor’s browser is blocked.
- CODE 424 – FAILED DEPENDENCY
This error code appears when the browser request failed due to the error of any previous request.
- CODE 426 – UPGRADED REQUIRED
This code appears when the browser must switch to a different protocol in order to make requests, such as switching to TLS / 1.0.
- CODE 428 – PRECONDITION REQUIRED
This message appears when the server needs the request to be conditional.
- CODE 429 – TOO MANY REQUEST
This error code appears when the visitor’s browser has made too many requests to the server in a certain period of time, that is, it has reached the limit of requests in that period of time.
- CODE 431 – REQUEST HEADER FILEDS TOO LARGE
This code appears when the server can not process the request because its header is too large, this error also appears when the sum of the size of all requests is too large.
- CODE 451 – UNAVAILABLE FOR LEGAL REASONS
This code is fairly new, it is used when content is not available because a court order has caused it to be deleted.
5XX CODES – SERVER ERRORS
5XX errors usually indicate errors on the server, ie errors that occur on the server even though the request sent by the visitor’s browser has been validated.
5XX errors often appear in PHP interpreter errors or errors in server configuration problems or even in an overabundance of resources.
- CODE 500 – INTERNAL SERVER ERROR
Error 500 or Internal Server Error is one of the most known errors since it is the most seen.
Code 500 indicates that the browser request failed to complete successfully because an unexpected error occurred on the server.
- CODE 501 – NOT IMPLEMENTED
This error is displayed when the server does not support some functionality or feature needed to respond to the visitor’s browser request.
- CODE 502 – BAD GATEWAY
The server is acting as a proxy or gateway or has a reverse proxy installed, but the reverse proxy or gateway has received an invalid response from the server, so it can not respond correctly to the browser request.
- CODE 503 – SERVICE UNAVAILABLE
This message is displayed when the server is unable to respond to the browser request because it is saturated or because maintenance is being performed and it is not accepting requests.
- CODE 504 – GATEWAY TIMEOUT
The server is acting as a proxy or gateway or has a reverse proxy installed, and the timeout has been exhausted by the request of the web server, so it can not respond to the request of the visitor’s web browser.
- CODE 505 – HTTP VERSION NOT SUPPORTED
This error is displayed when the server does not support the version of the HTTP protocol used by the visitor’s browser when making the request.
- CODE 509 – BANDWIDTH LIMIT EXCEEDED
This message is not standard, but even so, it is usually used a lot, especially on cPanel servers.
Error 509 indicates that the bandwidth limit has been reached and therefore the website can not be served.
- CODE 510 – NOT EXTENDED
This code is used when the request can not be processed because the server needs more extensions in order to process it.
- CODE 511 – NETWORK AUTHENTIFICATION REQUIRED
This code is used when the browser must be authenticated to be able to make requests, that is, to access the website you must authenticate.
- CODE 512 – NOT UPDATED
This code is not used too much and in many HTTP code listings it is not listed, but it is a code used to indicate that the server is in an update operation and can not accept connections.
Of all these HTTP codes, the most used or seen in common cases are the following:
- Error 404
- Error 500
- 301 Redirect
To give you an idea, 404 errors are errors that to fine tune the SEO of our website we must solve with 301 redirects as soon as possible.
The 500 errors must ALWAYS have them solved, this also includes errors 503 or 504 that can occur in some cases depending on the server.
These are the HTTP codes status we have to know about. These codes will help you to solve all your queries about your blog or website. I hope this article helps you in all the ways it can.
If you know any other HTTP code apart from these, mention them in the below comments.