What is an HTTP Request? Simply explained

The Hypertext Transfer Protocol (HTTP) defines the standard for transmitting web pages. It is a universal format through which a client like a browser communicates with a web server and establishes the structure of requests and data, enabling both sides to use a clear and efficient language. This allows information to be exchanged independently of the environment - for example, the operating system of a device. The HTTP Request initiates the connection between the two endpoints.

What is the HTTP Request?

The HTTP Request is a query that a user sends to a connected webspace or server. It consists of five elements:

• Start line with the chosen method, path, and HTTP version
• Additional URL parameters, if required
• Multiple header lines with detailed information such as browser and operating system
• Blank line as a separating marker between header and content
• An optional message with additional data

Formally, an HTTP Request consists of readable plain text using characters from the ASCII table. For example, when calling the website www.example.com, the crucial lines would look like this:

GET /index.htm HTTP/1.1
Host: www.example.com

This command instructs the server to retrieve the specified resource index.php from memory and send it to the client. With HTTP 1.1, a separate connection is established for each HTTP Request; however, since the introduction of 2.0 in 2015, these are bundled and transmitted simultaneously via a single header using Multiplexing. To optimize performance, efforts are usually made to minimize the number of requests.

What methods differentiate an HTTP Request?

There are several ways for a client to provide additional information to the server. These are known as methods and initiate an HTTP Request to define its structure and processing. The most common methods include:

• GET for retrieving content
• POST allows data to be sent to the server
• HEAD restricts the message to the header without content
• TRACE enables troubleshooting by reflecting and returning requests to the server
• CONNECT for establishing SSL tunnels on proxy servers
• PUT enables direct file uploads
• DELETE deletes an existing resource on the server

The most important methods among these are GET and POST, as they enable the retrieval of a webpage. They also serve for interaction by transmitting additional information, for example, to perform a search or fill out a form. Therefore, the HTTP request is not only for establishing a connection - it also determines the options a webpage provides.

What are URL parameters and what purpose do they serve?

Typically, websites use the GET method as it is both simple and versatile. It also allows for the transmission of additional information via URL parameters. These consist of a question mark as a delimiter, followed by additional data. This data is encoded in the URL format, allowing the transmission of special characters through different standards like UTF-8. However, a significant drawback is that URL parameters form a visible and unencrypted part of the address bar. Therefore, they are not suitable for sensitive information such as passwords, which should instead be appended to the header as additional data using the HTTP request POST. When the connection is secured via HTTPS, third parties cannot decrypt and intercept this information.

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