HTTP Headers 101: Things to Know

Browsing the web seems like such a simple process – all you have to do is open your favorite browser, type in your key phrase, and click on a webpage you want to open. There isn’t much to it. You’ll get the information you want in less than two seconds.

Of course, the simplicity of it is only surface-deep. What goes on in the background is a bit more complicated.

Your browser needs to communicate with the servers that store the information, the servers need to understand what the browsers want from them, and the two need to go back and forth until they present you with relevant information in an instant. All that is possible thanks to hypertext transfer protocols (HTTP) and common HTTP headers. They’re the cornerstones of the web, and they’re something you need to be familiar with if you want to improve your site’s and proxy server’s performance.

What are HTTP headers?

Hypertext transfer protocols were introduced by none other than Sir Tim Berners-Lee, the father of the world wide web. These protocols allow for a seamless transfer of data between servers and browsers (clients); however, they rarely stand on their own.

Hypertext transfer protocols use common HTTP headers to ensure that the client and the server have all the information they need to transfer data.

HTTP headers hold information regarding the server, your browser, your operating system, the requested page, the date and time of the request, your IP address, and much more. They define how your browser sends and receives information, how the servers process and handle your data (for example, Do-Not-Track settings), even how your connection is encoded.

While they’re optional, they’re virtually always included with the HTTP requests and responses. Still, you’ll never see them as the end-user since they’re part of the background processes.

How they are connected to servers and browsers

In essence, the entirety of the web is dependant on three primary agents:

  • Servers;
  • Browsers/clients;

Servers are physical storage devices (think computers, computer networks, dedicated machines) for all the websites, pages, pictures, and audio files available on the web. Without servers, you wouldn’t have any type of data available online.

Browsers/clients are software applications that enable you to access the information stored on servers. If you want to watch a YouTube video, access your email account, look up the weather forecast online, you need a browser like Chrome, Mozilla, or even DuckDuckGo to do so.

However, browsers and servers have no way to communicate with each other and share information on their own. That’s where hypertext transfer protocols and HTTP headers come in.

HTTP headers are essentially a language that both browsers and servers can understand. Browsers create HTTP headers to request information from servers; servers then read the HTTP headers and send a relevant HTTP response. The browser then relays the response and presents you with information in a readable format.

The main purpose of HTTP headers

The main purpose of HTTP headers is to pass more information between clients and servers. HTTP headers can specify your preferred language, for example, identify you as a unique client, detail your cookie preferences, authenticate your credentials if authorization is needed to access a site.

On the other hand, HTTP headers sent by the servers can contain information regarding the type and size of the content, cache storage options, date and time when the request was made, and more.

List of most used HTTP headers

Broadly speaking, HTTP headers belong to one of two categories – request headers (sent by the browser/client) and response headers (sent by the server). However, they can be further classified according to the information they carry. Here are some of the most common HTTP headers you’ll come across:

  • User-Agent HTTP header

User-Agent headers are designed to relay the information regarding your device as well as its operating system, software version, and more. As a general rule of thumb, they help the servers understand the type of HTML layout to present, which is why you’ll see the same webpage presented differently on PC, mobile, and tablets, for example.

  • Accept-Encoding HTTP header

Accept-Encoding headers tell the servers which compression algorithms to use if any. Compressing required information allows for faster transfers (aka faster load speeds) and enables servers to decrease traffic volume.

  • Accept-Language HTTP header

As previously mentioned, Accept-Language headers specify the client’s preferred language, usually based on the IP location.

  • Accept HTTP header

Accept headers tell the servers which data format to use when relaying information to the client – plain text, multimedia, PDF, etc.

  • Referer HTTP header

Referer headers notify the servers of where the client comes from – whether it’s directly from Google, a social media platform, a random blog, a news portal, or any place in between.

What they can be used for

The average user doesn’t typically have to pay mind to the HTTP headers as they’re usually inconsequential to them. However, businesses most commonly use HTTP headers in web scraping.

Most servers will work hard to prevent bots from accessing websites and webpages as they don’t bring valuable traffic. That’s why they’ll carefully assess all HTTP request headers and analyze where the traffic comes from, and block all suspicious users.

Obviously, that can hamper your web scraping efforts.

To bypass restrictions and accumulate data without hiccups, you’ll need to pay close attention to your HTTP headers and ensure that they make you seem like a typical, organic user. If you are keen to know more on the HTTP headers and their relation to web scraping, you can read the article here.


Although they can seem complicated, common HTTP headers are a simple information exchange between clients and servers. They enable seamless data transfers and allow you to browse with ease.

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