What Are HTTP Cookies and How Do They Work?

We all love cookies, but what about HTTP Cookies? Here, you will delve into the basics of HTTP Cookies, exploring what they are, how they can be used, and seeing both their advantages and limitations.
7 min read
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In detail, in this article, you will see:

HTTP Cookie Definition

An HTTP cookie, also known as a “web cookie,” “browser cookie,” or simply “cookie,” is a small piece of data that a server sends to a user’s web browser. After being received and stored on the browser, cookies are sent back to the server with each request. HTTP cookies generally contain information about the user’s activity and help maintain session state between different browsing sessions.

Keep in mind that HTTP is a stateless protocol. That means that the server treats each request as a stand-alone operation and has no memory of previous requests from the same user. Thus, it is necessary to send additional information with each request to maintain the state of a user’s session. This is exactly what cookies are about.

Specifically, the cookie mechanism starts when a website’s server returns an HTTP response with a Set-Cookie header. This header contains some data and an expiration date. When the browser receives a response involving a Set-Cookie header, it can store the cookie data in a text file or keep it in memory. Now, when the user visits a page on that website, the browser will send the cookie back to the server in the Cookie header of the request.

Cookies play a key role when it comes to providing a more personalized experience, maintaining login sessions, and tracking users. HTTP Cookies can also be used for security and authorization purposes.

Let us now look at use cases where HTTP cookies are especially useful.

Purpose of HTTP Cookies

HTTP cookies serve a variety of purposes. Let’s now jump into the three most important ones.

State/Session Management

HTTP cookies are used by websites to remember information about a user’s session. This information includes login sessions, search filters, the scroll position on a long page, and more. For example, when a user adds items to their shopping cart on an eCommerce website, this info is stored in a cookie. When the user closes the browser or visits another page, that valuable data is not lost but remains safe in the cookie saved on the disk.


Cookies can be used to store user preferences, such as preferred language, font size, and selected colors. This information is critical to personalizing the user’s experience on the website, making it more enjoyable and accessible.

Tracking Users

Cookies allow tracking the behavior of a user on a website, such as which pages they visit, how long they stay on a page, and which links they click on. This data can be studied to improve the overall user experience, adapting the content or layout of pages accordingly. Also, cookies are useful for collecting analytics data. For example, Google Analytics collects data and reports site usage statistics through a set of cookies.

Types of Cookies

As you just learned, HTTP cookies are useful in a variety of circumstances. As a result, there are many different types of cookies. Let’s take a look at the most important ones:

  • Session cookies: Are temporary and stored in memory by the browser. They only exist until the user closes their web browser. They are used to remember information about the user’s current browsing session on a website.
  • Persistent cookies: They are stored on the user’s hard drive and persist even after the web browser is closed. They are typically used to remember user preferences and maintain login sessions over time.
  • First-party cookies: Are set by the website that the user is visiting and are used to remember information about the user’s session and preferences.
  • Third-party cookies: Are set by a different website than the one the user is visiting and are generally used for advertising or tracking purposes. Examples are cookies from Google Analytics, Facebook.

HTTP Cookies: Pros and Cons

HTTP cookies are a versatile and powerful tool that covers various needs. However, they also come with some drawbacks to consider. It is time to dig into the main pros and cons of HTTP cookies.


  • Easy to implement and use: Cookies are a simple and effective way for maintaining session state over HTTP.
  • Can be stored on disk: Persistent cookies allow data from the previous browsing session to be retained, even after closing the browser.
  • Can be shared between pages and domains: The same cookie can be used by several pages of the same site and by different subdomains of the same domain.


  • Limited in size and number: Most browsers limit browser size to 4 KB and allow no more than 150 cookies per domain.
  • Can be deleted by users: Cookies can be deleted by users at any time directly in the browser, which can cause problems for websites that rely on them.
  • Security/Privacy risks: Cookies can contain sensitive information about the user and pose a security risk. Additionally, cookies can be used to track and collect data on a user’s behavior, which raises privacy concerns.

Cookies in Web Scraping

When it comes to web scraping, it is essential that the data retrieval script behaves similarly to a human being. Otherwise, the anti-scraping technologies adopted by many websites may identify your scraping script as a bot and block it accordingly.

Do not forget that it is the server that instructs the browser to create cookies. So, it is the server itself that expects these cookies in the HTTP requests. Not receiving cookies would mean that the request is suspicious, and the server might decide to block it. By setting the right cookie, web scrapers crawl web pages without raising suspicion.

Also, keep in mind that cookies contain information about a particular user’s session. Thus, by forging proper cookies, you can fool the server into believing that each request is coming from a different user. This will make your web scraping script more difficult to identify, track, and block.

Dealing with cookies when scraping data from the Web is critical, but not easy. That is why you should rely on an advanced, fully-featured, modern scraping tool such as Bright Data’s Web Scraper IDE. With such a tool, you can easily manage HTTP cookies.

In detail, Web Scraper IDE will help you extract tons of data from the Web while bypassing all the anti-scraping technologies, such as CAPTCHAs. Also, Bright Data directly offers off-the-shelf, high-quality datasets. Buy them to have access to an impressive amount of data. For a proxy optimal cookies solution you can use Bright Data’s Web Unlocker where you can stay undetectable with an expanding repository of site specific browser cookies.


In this article, you learned what HTTP cookies are, why and when they are useful, and how to use them for web scraping. Cookies are small text files stored by the web browser and used to remember information about your browsing session. As you saw here, they come in handy in a variety of scenarios and use cases. At the same time, they also bring some challenges and concerns. In particular, dealing with them when it comes to web scraping may not be easy.

For this reason, you should consider a web scraping solution such as Web Scraper IDE, which comes with everything you need to effortlessly scrape data from the web. You can directly purchase one of the several complete datasets available on Bright Data. Otherwise, you should consider to use Web Unlocker as a 99.9% success rate solution.