What are HTTP cookies and how they affect web scraping?
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Iveta Vistorskyte

Sep 13, 2020 6 min read

HTTP cookies are not a new thing in the tech world, but they raise many questions among users and, in some cases, for developers. First of all, many people think that HTTP cookies are a tool for spyware. Second of all, in terms of web scraping, HTTP cookies can be the reason for getting blocked by targeted web pages.

In this article, we will explain the basics of HTTP cookies and how they work. In the second paragraph of this article, we will take a closer look at web scraping basics and where HTTP cookies can impact a smooth web scraping process.  

What are HTTP cookies?

HTTP cookies are small amount of data that a web server sends to the user’s web browser. With later requests, the browser saves it and sends it back. HTTP cookies are an essential part of web development. Without them, many web pages would simply be worthless.

What is the purpose of changing this small piece of data between the user’s browser and the web server? The answer is pretty simple – for a web server to remember information about users and identify them from others. Cookies do not need to get personal information. They are enough to remember browsers specifications that allow websites to separate users from each other. Although some sites use cookies to store more personal data, this can only be done if users agree to provide their personal information.

HTTP cookies recognize users by their browsers
HTTP cookies recognize users by their browsers

What do HTTP cookies do?

In most cases, cookies are necessary for websites that need logins, have customizable themes, and other advanced features. To dig deeper into what a cookie does, the main reasons sites use them are personalization, tracking, and session management. Let’s take a closer look into each of these reasons for a better understanding of why this is important. 

Session management. A session is an interaction that users have with a single website. This includes actions such as logins, adding products to shopping carts, and much more. HTTP cookies store this data so that the user does not have to continually log in to their account or, in case of an accidental shutdown of the page, save items in the cart.This facilitates users’ web browsing because they do not have to waste their time on repetitive actions.

Personalization. HTTP cookies enable the user to access the website according to general characteristics such as language, browser type used to access the service, location from where the service is accessed, and much more. Websites are able to adapt the content so that users can smoothly navigate the page.

Tracking. Cookies help a website to adapt content to match a user’s preferred interests. For example, news portals use HTTP cookies to classify content according to what users are interested in.

Furthermore, there are so-called third-party cookies that usually are used for advertising. According to browsing history over a long time, these cookies help adapt advertisements that match a user’s preferences. These advertisements can annoy users because they feel that everytime they are tracked. However, people are not obliged to see these advertisements because they can delete these HTTP cookies. We will not expand on this topic, but you can find suggestions on how to stop third-party cookies from tracking your browsing activity with a quick Google search.

How are cookies sent?

Web server set cookies in the HTTP header. When a user’s browser sends HTTP requests to a web server, the browser adds cookies to every request to the same domain. The cookie file is stored in the user’s browser application data folder. Later, the browser automatically sends this cookie as part of the request.

This is how webpages recognize users by their browsers. Then the web server can personalize the content, store required data for users (like logins, products in the cart, etc.), and much more.

HTTP cookies help to personalize content for users
HTTP cookies help to personalize content for users

HTTP cookies in web scraping

The main challenge in web scraping is how to avoid being blocked by targeted web pages. Understanding how cookies work can be one of the solutions to solve this problem.

In web scraping, one of the essential parts is to mimic human-like behavior. Otherwise, web servers can identify web scraping as suspicious bot activity, and a chance of being blocked arises. Even if web scraping activity is not blocked, you can get error responses from targeted websites.

As we already mentioned before, HTTP cookies are sent from a website. In this case, it is essential to think of HTTP cookies management. When making requests to required web pages, the right cookies need to be used to access the required data. If you access some page within a website and your request does not contain cookies from the main page, there is a big chance that your web scraping activity would be identified as suspicious.

One of the solutions to how to manage HTTP cookies when you need to access, for example, a specific product on an e-commerce site, is to enter the main page firstly, collect the cookies and send them with your requests for particular products. By using the right cookies, developers can imitate a completely different user on every request they make. The most important part is that every Python library you would use to make requests (e.g., Requests, PycURL) has some built-in HTTP cookie management.

HTTP headers are an essential part of web scraping process
HTTP cookies are an essential part of web scraping process

Wrapping it up

The main purpose of HTTP cookies is to identify users that websites would be able to adapt their content for users to keep important information for users such as logins, items in the cart, and much more. HTTP cookies do not identify personal information because they are created to identify browsers.

Neatly cookie management is a part of a smooth web scraping process. Otherwise, there is a possibility that the web scraping process will be unsuccessful, and the required data will not be accessible.

If you are interested in the data gathering process, we suggest you check out how to set the right approach to web scraping. Furthermore, if you are interested in starting web scraping, the Python web scraping tutorial will be an indispensable guide.

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About Iveta Vistorskyte

Iveta Vistorskyte is a Copywriter at Oxylabs. Growing up as a writer and a challenge seeker, she decided to welcome herself to the tech-side, and instantly became interested in this field. When she is not at work, you'll probably find her just chillin' while listening to her favorite music or playing board games with friends.

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