Get to know HTTP Status Codes: Definition and Complete List

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HTTP status codes are like short notes from the server attached to a web page. HTTP status codes are not actually part of the page content itself. Instead, HTTP status codes provide messages to the server to tell the user how the page looks like when it receives a request to view a particular page.

This kind of message pops up every time a website interacts with the server, even if you don't see it. If you are a website owner or a developer, understanding HTTP status codes is very important. Because when messages like these appear, HTTP status codes are invaluable tools for checking and fixing erroneous website configurations.

In this article, we will introduce some server statuses and error codes, and explain what's going on behind a working server. Let's start guys!

What are HTTP Status Codes?

Every time you click on a link or type in a URL and press Enter, the search engine will send and process a request to the web server on the page being accessed. Meanwhile, the server will receive and process the request, and then send back the relevant source with the HTTP header.

HTTP status codes will be sent to Search Engines in HTTP headers. When status codes are returned every time the browser tries to send a request on a web page, you often won't see them.

But usually when a problem occurs, you will see HTTP status codes displayed on the browser screen. This is the server's way of saying: “An error occurred. This is the code that will explain what went wrong on that server.”

HTTP Status Codes Class Types

HTTP status codes are divided into five classes. This is a method of grouping on responses that have the same meaning. Knowing what the status codes are, will certainly help you quickly decide on a repair method.

Here are the five classes in the HTTP status code:

1. 100s: Code information indicating that the request from the browser is running.
2. 200s: The success code returned when the browser request is received, understood, and processed by the server.
3. 300s: A redirect code returned when a new source has been substituted for the requested resource.
4. 400s: Client error code indicating a problem with the request.
5. 500s: The server error code indicates that the request was received, but there is an error on the server preventing the request from being fulfilled.

In each of these class types, there are various server codes that may be returned by the server. Each of these codes has its own specific meaning, which we will further discuss below.

Complete List of HTTP Status Codes

The following is a list of HTTP status codes that are often experienced by most browser users, including:

1. 100 Status Codes

The level 100 status code indicates that the request to the server is still in progress. Actually this is not a problem, the code only provides information to the user regarding what is happening in the browser that is running.

• 100: Continue

This code means to indicate that the server has received the browser header request and is now ready to send it as well. This makes request processing more efficient as it prevents the browser from sending page requests even though the headers have been rejected.

• 101: Switching Protocols

The user's browser asks the server to change the protocol and the server complies.

• 103: Early Hints

Code 103 indicates returning a response header before the server response is fully ready.

2. 200 Status Codes

This code is one of the codes that users often receive. This response indicates if the browser is running properly.

• 200: Everything is OK

This code will be sent when a web page or resource is working properly.

• 201: Created

The server has fulfilled the browser's request and as a result, the browser generates an updated resource.

• 202: Accepted

The server has received the browser request and is still processing it. However, the request may not eventually result in a perfect response.

• 203: Non-Authoritative Information

This status code will be present when the proxy is used. That means the proxy server received the 200 “Everything is OK” code from the original server, but has modified the response before sending it to the user's browser.

• 204: No Content

This code indicates if the server has successfully processed the request, but will not return any content.

• 205: Reset Contents

Like code 204, this code means that the server has processed the request but will not return any content. In addition, code 205 also requires the browser from the user to reset the document view.

• 206: Partial Content

You may see this code if the browser uses range headers. This allows the browser to resume paused downloads, as well as split downloads into multiple parts. Code 206 is sent when the range header causes the server to send only a portion of the requested resource.

3. 300 Status Codes

Redirection is a process used to communicate that a resource or page has been moved to a different location. There are several HTTP status codes in these redirects, to provide information to visitors regarding where to find what they are looking for.

• 300: Multiple Choices

Sometimes, there may be several possible resources that the server can respond to fulfilling the browser request. A status code of 300 means that the browser must choose between the two. This can happen when there are multiple file type extensions available, or if the server has an undefined definition of a word.

• 301: The requested resource has been permanently moved

This code is sent when the web page or resource has been permanently moved to a different resource. Thus, the code is used for permanent URL redirects.

• 302: The requested resource has moved, but was found

The code indicates that the request on the resource was found, but not at the location it should be. Code 302 is usually used for temporary URL redirects.

• 303: See Other

To understand the 303 status code, you must first know the difference between the four basic HTTP request methods. Basically, the 303 code tells the browser that they found the requested resource via POST, PUT, or DELETE. However, to get it using GET, you have to make the correct request for a different URL than the one previously used.

304: The requested resource has not been modified since the last time you accessed it

This code informs the browser that the resource stored in the browser cache has not changed. It is used to speed up the web page delivery process by reverting to previously downloaded resources.

• 307: Temporary Redirects

This status code replaces the 302 'Found' code as the action when the source is currently being temporarily moved to a different URL. Unlike the 302 status code, this code does not allow changing the HTTP method.

• 308: Permanent Redirects

Status code 308 is the successor to code 301 'Moved Permanently'. They don't allow changing the HTTP method and indicate the request at the source has now moved permanently to the new URL.

4. 404 State Codes

At level 400, these HTTP Status Codes start to provide little information regarding the errors that have occurred. This is an error code indicating that an error or request occurred to the browser.

• 400: Bad Requests

The server was unable to return a response due to an error in the user's browser

• 401: Unauthorized or Authorization Required

This code is returned by the server when the target source lacks authentication credentials.

• 402: Payment Required

Initially, this code was used as part of a digital payment system. However, it didn't work as it should. Ultimately, this code is used by various platforms to indicate that the request could not be fulfilled, usually due to a lack of funds. Here's an example of when this code appears in the user's browser:

a. The user has reached the daily request limit on the Google Developers API.

b. The user has not paid the Shopify fee and the online store is temporarily deactivated.

• 403: Access to that resource is forbidden

This code is returned when the user tries to access something they do not have permission to view. For example, when a user tries to reach password protected content without properly logging in. The server will then send a 403 error code.

• 404: The requested resource was not found

This is the most common error message that users often encounter. This code means that the requested resource was not found, and the server doesn't know if the resource ever existed.

• 405: Method not allowed.

It is created when the hosting server (origin server) supports the accepted method, but the target source does not.

• 406: Not acceptable response

The requested resource is only capable of producing unacceptable content according to the headers sent in the request.

• 408: The server timed out waiting for the rest of the request from the browser

This code appears when the server times out while waiting for a complete request from the browser. In other words, the server does not receive the complete request sent by the browser. One possible cause is network congestion resulting in lost data packets between the browser and the server.

• 409: Conflicts

The 409 status code means that the server was unable to process the browser request because there is a problem with the intended source. This code also sometimes appears because editing is done simultaneously.

• 410: The requested resource is gone and won't be coming back

This code is similar to the 404 'Not Found' code. However, this status code 410 indicates that the condition is permanent.

• 411: Length Required

This response code indicates that the server refuses to accept the request without the Content-Length header specified. This means that the requested resource requires the client to specify a certain Content-Length in order to access it.

• 412: Preconditions Failed

This code appears when the user's browser includes certain conditions in its request headers, and the server does not meet those specifications.

• 413: Payload Too Large

This status code indicates if the browser request is larger than the server can process.

• 414: URL Too Long

Code 414 appears as the result of a GET request that has been encoded as a query that is too large for the server to process.

• 415: Unsupported Media Type

The request sent includes a media type that is not supported by the server or source.

• 416: Range Not Satisfiable

The 416 status code indicates that the server was unable to fulfill the request. For example, a user requests a document that is 800-900 bytes long, but turns out that the document is only 200 bytes long.

• 417: Expectations Failed

The server cannot meet the requirements specified in the header of the request.

• 418: I'm a teapot

This unique code is represented by a teapot that accepts requests to brew coffee. This one HTTP Status Codes indicates that the server refuses to process the request.

• 422: Unprocessable Entities

The user request contains a semantic error and the server is unable to process it.

• 425: Too Early

This code is sent when the server is not willing to process the request because maybe the user is reloading the intended page.

• 426: Upgrade Required

HTTP Status Codes client error response codes indicate that the server refuses to perform the request using the user's current protocol, but may be willing to do so after the user upgrades to a different protocol.

• 428: Precondition Required

Indicates if the server requires more specific terms or conditions before processing the request.

• 429: Too many requests

The code is generated by the server when the user has sent too many requests in a certain time. This can sometimes happen due to bots or scripts trying to access the site.

• 431: Request Header Fields Too Large

The server cannot process the request because the header field is too large. This may indicate that there is a problem with some or all of the headers on the page or website you are referring to.

• 451: Unavailable for Legal Reasons

The server operator has received a request to prohibit access to the resource requested by the user.

• 499: Client closed request

This code is returned by NGINX when the user closes the request while NGINX is processing it.

5. 500 Status Codes

The 500 level status code is also a code indicating an error. However, this code indicates that the problem is behind the server. This can make them more difficult to complete.

• 500: There was an error on the server and the request could not be completed

This is a common code that indicates an internal server error. There was an error on the server and the requested resource was not sent. This code is usually generated by a third party plugin, faulty PHP, or even a corrupted database connection.

• 501: Not Implemented

The code indicates that the server does not support the functionality required to fulfill the request. This is almost always a problem in the web server itself and usually needs to be resolved by the website owner.

• 502: Bad Gateways

This code usually means that one server has received an invalid response from another, such as when a proxy server is in use. This code also sometimes appears when a query or request will take too long, so it is canceled or killed by the server and the connection to the database is lost.

• 503: The server is unavailable to handle this request right now

Indicates if the request cannot be completed at this time. This code may be returned by a server that is overloaded and unable to handle additional requests.

• 504: The server, acting as a gateway, timed out waiting for another server to respond

This is the type of code returned when there are two servers involved in processing a request, and the first server times out while waiting for the second server to respond.

• 505: HTTP Version Not Supported

The server doesn't support the HTTP version used by the user to make the request.

• 511: Network Authentication Required

This status code is sent when the network used by the user requires some form of authentication before sending the user's request to the server. For example, when you need to agree to the terms and conditions of a public Wi-Fi hotspot.

• 521: Web server is down

Error code 521 is Cloudflare specific error information. This means the user's web browser successfully connected to Cloudflare, but Cloudflare was unable to connect to the originating web server.

• 525: SSL Handshake Failed

HTTP Status Codes 525 indicates an SSL handshake between a domain using Cloudflare and the originating web server failed.

Conclusion

Even though they look confusing and intimidating, HTTP Status Codes are actually very informative, you know! So, knowing the types of codes can help you solve the problems you face when surfing search engines. 

Understanding response code is very important for website maintenance as it is also related to Search Engine Optimization. Hope this article can help you..!!