Every day the Internet is used by millions of people for all kinds of things. Usually we enter an Internet address or URL and receive our website. However, sometimes an error occurs. The web page is not displayed and a status code is output, which indicates the error. However, many users do not understand the meaning of these codes, although they say a lot about what happened.
What exactly are HTTP Status Codes?
An HTTP Status Code is a code that is issued by a web server to the web browser to transmit certain information. The codes are mainly used to tell the browser how to deal with a request or to give feedback on a request. The ordinary user usually notices such a status code whenever something is not working. One of the best known status codes is the Error 404 page not found. However, the status code is not only displayed when errors occur. Even if an operation was successful, a user is redirected, or if a variety of other actions and measures are executed on the server, these are transmitted to the browser in the context of status codes. In most cases, however, you as an ordinary user will not notice anything.
The Status Code Groups
All HTTP Status Codes are divided into six groups, which are numbered from one to six and nine, each of which refers to a specific category of messages. Generally the groups are assigned as follows:
* 1xx outputs general information
* 2xx contains the codes for successful operations
* 3xx contains the codes for redirection and forwarding
* 4xx is responsible for the client errors
* 5xx is responsible for server errors
* 9xx outputs proprietary errors
These six groups contain all status codes for the HTTP protocol. Each group contains a different number of codes that indicate a specific situation, state or status.
The 1xx Group - General Information
This group comprises three statuses, namely status codes 100, 101 and 102, which are responsible for the output of general information and notes. For example, code 100 returns a Continue command to the browser, telling it that it can continue with a potentially large and server-heavy request. Code 101, on the other hand, tells the browser that the protocol is being changed, e.g. when switching from HTTP to FTP, etc. Finally, code 102 stands for Processing and tells the browser that the request is still being actively processed. In this way, a timeout is prevented. The codes in this category are used exclusively for communication with the browser, so that you normally do not notice anything.
The 2xx Group - Successful operations
These codes are purely informative. The states in this category give simple feedback, such as OK that a form has been submitted, or that a page deliberately contains no content. In most cases, as a normal user, you do not notice these codes and do not need them.
The 3xx Group - Forwarding
The group of 300 codes deals exclusively with diversions. They contain feedback, for example on permanent redirection, proxy use, etc. Their main purpose is to make the browser aware of these redirections and to point to the correct URL or path. As a user, you will usually get nothing or very little from the status codes of this group.
The group 4xx - Client error
The 400 group is the first group that deals with current error messages. In this case, these are client errors, that is, problems caused by the client, that is, the Web browser, or errors triggered by the client. The number of different error codes is considerable, but the ordinary user usually encounters mainly three codes from this group, namely the 400, the 403 and the 404.
The Error 400 - Bad Request stands for a faulty request. Here the browser has requested a function or a page. However, the request was incorrectly structured and could therefore not be executed by the server. Also often you get the Error 403 - Not Allowed. This error always occurs when you go to a website for which you have no access. For example, if you want to access a server directory without the appropriate rights, or enter the wrong access data in a .htaccess query, you will get this error message. By far the most common error is Error 404 - Not Found. Whenever you enter an invalid or wrong web page, an Error 404 is the answer.
The 5xx Group - Server Error
If the 400 group stands for client errors, i.e. errors caused by the web browser, the 500 group stands for the opposite. It returns error messages that were triggered by the server or caused on the server. Probably the best known error is Error 500 - Internal Server Error. This is a collective error message for a number of server errors that do not have their own code and are not specified in more detail. Other common server errors include Error 502 Bad Gateway, such as when a bad proxy is used or forwarding fails, and Error 503 Service Unavailable, when a server is temporarily unavailable, for example, due to maintenance. Occasionally you will also encounter an Error 504 Gateway Timeout, which tells you that the connection has been terminated due to a timeout. Especially on important websites or special offers, you will also encounter Error 509 - Bandwidth Limit Exceeded more often. This message indicates that the request was aborted because otherwise the Bandwidth of the server would have been exceeded.
The 9xx Group - Proprietary status messages
The 900 group is completely reserved for own, so-called proprietary error messages. It should be server Administrators and webmasters to develop and use their own error messages and status codes. For this reason, the use of statuses can vary from server to server and from configuration to configuration. An explanation of the codes or a statement about which codes are used can therefore also not be made.
