HTTP requests: methods, syntax, and ex­pla­na­tion

On the Internet, browsers com­mu­ni­cate with web­servers known as the HTTP protocol. This protocol controls how the client for­mu­lates a request and how the server responds to them. The HTTP protocol has different HTTP methods. It is worth knowing the most common ones among them. This article explores the details of the in­di­vid­ual HTTP request methods, also often known as HTTP verbs.

GET is the "ancestor" of HTTP requests. This HTTP verb has existed since the beginning of the World Wide Web. It is used to request a resource - such as an HTML file - from a webserver.

When you enter the URL: www.example.com into your browser, it connects to a web server and sends a GET request:

The file index.php in this example is simply the homepage which is sent from the server to the browser.

Similarly, re­quest­ing the test.html file from the URL www.example.com/test.html would be for­mu­lat­ed like this:

In this case, the server will return the test.html file.

Ad­di­tion­al in­for­ma­tion can be added to the GET request for the web server to process. These URL pa­ra­me­ters are simply appended to the URL. The syntax is very simple:

• The query string is in­tro­duced with a question mark (“?”).
• Each parameter is named, so it consists of a name and a value: "Name=Value".
• If several pa­ra­me­ters are to be included, they are connected using an ampersand ("&").

Here is an example. On the website of a software company, "Windows" is entered as the platform and "Office" as the category in order to receive cor­re­spond­ing offers from the server:

Query strings require a special character encoding because many special char­ac­ters have a unique meaning. For example, the text "HTTP Overview" must be encoded as follows to be accepted as a query string:

If you want to send large amounts of data such as images or share con­fi­den­tial data with the server, the GET HTTP verb is not ideal because all the data you send is written in the browser's address bar without en­cryp­tion.

In this case, the POST method is more ap­pro­pri­ate. This method does not write the URL pa­ra­me­ters to the URL, but adds them to the HTTP header.

POST requests are mostly used in con­nec­tion with online forms. Here is an example of a form that takes the name and e-mail address and sends it to the server using POST:

The HEAD HTTP method is used to query the response header without sending a file im­me­di­ate­ly. This is useful, for example, if large files are to be trans­ferred: Thanks to the HEAD HTTP request, the client can first receive in­for­ma­tion on the file size, and only then decide whether they want to receive it.

Example:

With the OPTIONS method, the client can query which methods the server supports for the file in question.

In the field "allow", we learn that the server supports the methods OPTIONS, GET, HEAD, and POST. In the field "content-length", the number “0” tells us that no file was trans­ferred, only the header.

The TRACE method can be used to trace the route that an HTTP request takes to the server and back to the client. You can use the tracert command on Windows to track this route yourself. To do this, enter the following command in the command line (cmd.exe):

Some methods are only ap­plic­a­ble in con­nec­tion with specific con­fig­u­ra­tions. These include the CONNECT HTTP verb, which es­tab­lish­es a direct, protected con­nec­tion via a proxy (tunneling), and various methods in con­nec­tion with WebDAV: PATCH, PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, LOCK, and UNLOCK.

PUT, PATCH, and DELETE are used to save, change or delete files on the server. For tra­di­tion­al website pro­gram­ming, these methods play only a minor role, as they are blocked by the servers for security reasons. They are used in the WebDAV context and in con­nec­tion with the REST-API.