HTTP Request Header


An HTTP Request Header is a component of an HTTP (Hypertext Transfer Protocol) request that provides additional information to the server about the client’s request. It consists of key-value pairs that convey details such as the preferred content type, language, and encoding among others. The server uses this information to customize and optimize the response, enhancing the user’s experience.


H T T P R i k w e s t H e d ə r

Key Takeaways

  1. HTTP Request Headers are key-value pairs of information sent by the client to the server in an HTTP request. They help the server understand important details about the request.
  2. Common headers include ‘Host’, ‘User-Agent’, ‘Accept’, ‘Referer’, and ‘Cookie’, among others. These headers convey critical information, such as the domain receiving the request, the client’s browser, and the preferred content type.
  3. Custom headers can also be added, typically prefixed with ‘X-‘, to communicate additional data or requirements between the client and server. Custom headers should follow the standard header naming conventions.


The HTTP Request Header is an essential element in web-based communications, as it carries vital information between a client and a server during the exchange of data.

When a user’s browser submits a request for a web page or a resource, it sends multiple HTTP headers containing details about the request, such as the type of browser, accepted data formats, and language preferences.

This enables the server to process the request effectively, tailoring its response according to the client’s specific needs and capabilities.

In essence, the HTTP Request Header plays a crucial role in facilitating smooth and efficient communication between browsers and web servers, ultimately rendering a seamless browsing experience for end-users.


HTTP Request Header serves a crucial role in establishing effective communication between a client and a web server. The primary purpose of the request header is to provide valuable information about the client, such as the browser being used, user preferences, and other data, so that the server can process and tailor the response accordingly. This allows for a more seamless and personalized interaction between the user and the server.

The request header also includes information about the type of content requested, accepted languages, character sets, and compression methods supported by the client, which enables the server to return appropriate content conforming to these specifications. Moreover, the HTTP Request Header contributes significantly to the efficiency and security of web transactions. For example, cookies are sent via the request header, allowing website authentication and session management processes to work smoothly.

In addition, certain headers enable caching mechanisms, which help reduce server load and improve data retrieval performance for users. Some headers also work to protect against common web security risks, such as Cross-Site Request Forgery (CSRF) and clickjacking attacks, by providing control over content and resource sharing between different origins. Overall, the HTTP Request Header plays a vital role in enhancing user experiences, optimizing resource usage, and maintaining security on the web.

Examples of HTTP Request Header

HTTP (Hypertext Transfer Protocol) request headers are key-value pairs that provide information about the client, the requested resource, and other preferences set by the user. Here are three real-world examples of HTTP request headers:**User-Agent:**The User-Agent header field provides information about the client software (like browser or mobile app) that is making the request. For example, when you connect to a website using Google Chrome, the User-Agent header may appear like this:`User-Agent: Mozilla/0 (Windows NT

0; Win64; x64) AppleWebKit/36 (KHTML, like Gecko) Chrome/82 Safari/

36`This tells the server that the request is coming from the Chrome browser on a Windows 10 operating system, which helps the server in serving up content suited to that browser platform.**Accept-Language:**This header field indicates the user’s preferred language(s) in which they would like to receive the response. For example, if a user is accessing a website and prefers English (US) as their language of choice, the Accept-Language header would look like this:`Accept-Language: en-US,en;q=9`This enables the server to deliver content compatible with the user’s language preferences, if possible.

**Referer:**The Referer header field indicates the URL of the webpage that the user is navigating from, providing information about how the user arrived at the requested resource. For example, if a user clicked a link on a blog that leads to another site, the Referer header would look like this:`Referer:`This information helps website administrators understand how visitors are interacting with their site, track user behavior, and optimize the user experience.

FAQ – HTTP Request Header

What is an HTTP Request Header?

An HTTP Request Header is a set of key-value pairs sent by a client to a server as part of an HTTP request. It provides additional information about the request, such as client capabilities, preferred languages, and authentication data. Servers use this metadata to process the request and generate an appropriate response.

What are some common HTTP Request Headers?

Some commonly used HTTP Request Headers include:

  • User-Agent: Provides information about the client’s browser and operating system.
  • Accept: Specifies the media types the client can accept.
  • Accept-Language: Indicates the client’s preferred language for the response.
  • Host: Contains the domain name of the server the request is being sent to.
  • Authorization: Carries authentication information for requests requiring credentials.

How do I set custom HTTP Request Headers?

To set custom HTTP Request Headers, you can use APIs and libraries available in various programming languages. For example, in JavaScript, you can use the XMLHttpRequest or Fetch APIs. In Python, you can use the requests library. These tools allow you to set custom headers before sending the request to the server.

What is the purpose of the Host header?

The Host header is required by HTTP/1.1 and later versions. It specifies the domain name and, optionally, the port number of the server to which the request should be directed. This allows a single physical server to host multiple websites by distinguishing between them using the Host header value.

Can HTTP Request Headers be modified during a request?

Once an HTTP request has been sent, its headers cannot be modified. However, you can intercept and modify the headers before the request is sent, using middleware or browser extensions like browser developer tools. This can be useful for debugging, testing, and modifying request headers for security or compliance reasons.

Related Technology Terms

  • HTTP Response Header
  • User-Agent
  • Content-Type
  • Accept-Encoding
  • Cache-Control

Sources for More Information


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