What Is a Cookie on a Website? A Complete Beginner's Guide

Have you ever gone to a website and been straight away asked to ‘Accept Cookies’? Most people click ‘Accept’ without a second thought, just to get the message out of the way. Yet have you ever considered what cookies are on a website? Why do sites ask you to accept cookies, or are they something you should be concerned about? A cookie is a small text file that your browser saves whenever you visit a website. It helps a website recognise your browser or session when you return. 

The website you have just been to keeps this information and calls it up whenever you visit it again. To sum up, cookies allow websites to remember things such as your login details, the items in your shopping cart, and your preferences. Although they are useful, some cookies can also gather data that might impact your privacy. In this guide, you will find out what website cookies are, how they function, why websites use them, the various types of cookies, and how to handle them safely.

Cookie Meaning — The Simple Definition

Here is the simplest definition of what cookies are. Cookies are pieces of text sent to your browser when you visit a website. They are also known as “HTTP cookies”, “browser cookies”, or “web cookies”, which are specifically made for web browsers to track, personalise, and save information about each user’s session. However, they have one more basic job, which is to remember your activities performed on a website.

Moreover, cookies can also remember the content you are looking for on a website, your login details, or whether it is a piece of text written while filling out a form. This is how cookies work for a website: they collect and remember the information of each individual while we visit that website again. 

To put it simply, it is a bit like getting a ticket for a coat-check:

• You hand over your “coat” to the cloak desk: It means that when you often connect/visit a website, a pocket of data is linked to your device on the server side, which a user can’t see. This could be your personal details(like sign in or sign out), your shopping cart, or even the number of pages you have visited.
• You get a “ticket” to identify you as the “coat” owner: The cookie(containing the data) is then given to you and is stored in your web browser. It has a unique ID for each of us because no user has the same ID as yours.
• If you leave and return, you can get the “coat” with your “ticket”: Suppose you revisit the website at the same time; your browser sends the cookie back to your website. The website reads the unique ID in that cookie and reassembles you on your last visited page of that website, as if you never left.

What Are Website Cookies Used For?

I always wonder what website cookies are and how they work on a web server. They are used to remember the user and can save information and customisation settings. So that a user doesn’t need to start and register again from scratch when they open the web browser. 

• Website cookies let users shop online, stay logged in, and enjoy personalised web content. 
• For website owners, cookies let you understand user requirements and serve them a better experience online. A well-structured website can also make these interactions easier for visitors, especially when following the principles of what makes a good website. 
• Cookies are also at the centre of a larger debate regarding privacy, personal data security, and user tracking across the internet. For users accessing websites across different screen sizes and devices, responsive design can also play an important role in creating a consistent browsing experience. 

Session Management — staying logged in, keeping your cart intact

Session management handles creating, validating, editing, storing, and ending users’ sessions. It’s the system that allows websites and apps to remember users as they navigate from page to page. It ensures that user actions—like adding items to a cart, checking bank balance, or editing a document—are tracked and linked to the correct user. 

Thus, session management protocols help to preserve the confidential user identity and remember authorised users, preventing their data from falling into the wrong hands. This is one of the many functions involved in web development. 

Personalisation — remembered preferences, language settings, tailored content

Personalisation helps to meet digital preferences by using remembered preferences, language settings, and tailored content to fit according to user needs, which makes users’ experiences smooth.

Core elements of personalisation are as follows: 

• Remembered preferences: The devices save your choices like dark mode, frequently used applications or tools, and/or saved home and work addresses so that a user doesn’t need to re-enter them after revisiting the web page or that specific content.
• Language settings: Several platforms detect or apply your native language preferences across your interfaces, such as managing your Google account, regional settings, and during the usage of social media accounts.
• Tailored content: Algorithms suggest articles, products, and search results based on your recent activities or immediate context.

Tracking & Analytics — how sites learn browsing behaviour, targeted ads

Tracking: Cookies track multiple visits to the same site over time and read user activity. Some online merchants, for example, use cookies to track the visits of a specific user, including their interests and searched products.

The information they get allows them to suggest other items according to their choices, which attracts them. Later on, a profile is built on that user’s browsing history on that website.

“Targeted advertisement” or “data-driven targeting” is a form of advertisement, including online marketing, which can influence the audience with certain traits, based on the products, choices, or interests and the person or advertiser who is promoting.

How Cookies Actually Work

The system corresponding to cookies is the communication between the web server and the user’s web browser. When a user searches for something specific in the web browser, then clicks on a link and enters a web page, the server creates a small piece of data called an HTTP cookie and sends it to the browser. The browser stores the user’s information and then sends it back to the same website that you visited, which helps them identify the user and their requirements for future visits. 

Now, let’s understand how browser-server exchange works step-by-step:

• The Request: When you enter a URL of a website, your browser sends an HTTP request to the web server asking for the resources of the website.
• The Generation: Then the server processes the request and creates the unique identifier(a cookie) specifically for your session until it ends.
• The Response: The server includes the cookie in the HTTP response using the Set-Cookie header, which tells the browser to save it.
• The Storage: Your browser receives the response, renders the page, and automatically stores the cookie locally on your device.
• The next visit: When the user revisits the same website, the browser sends new HTTP requests to the server to indicate that the user is revisiting.
• Browser automatically sends the cookie: As per the request, the browser includes the cookie stored in the cookie header, allowing the server to recognise the user’s session.
• Server identifies revisitor: After this, the server reads the unique identity of the user and remembers the user identity, login status, and preferences in the shopping cart without starting it from scratch.

Understanding where website data is stored is also useful when considering web hosting and how websites manage information between the browser and server. 

“Name-value” pair:

One more thing that needs to be covered in this section is the “name-value” pair, in which the name tells the browser which cookie is for and the value holds the actual data. A cookie also includes some details like an expiration date, path, domain, and secure connections (HTTPS).

For example:

UserID = 87362ABC

In most cases, the value is just a unique ID, not personal information. So instead of storing something like:

Name = John

Password = ****

the site may store:

SessionID = X93KLM82

When the browser sends that cookie back, the server matches the ID with its database and finds the right user or session.

Background of cookies

The term cookie was made up by the web-browser programmer r Lou Montulli. It was derived from the term magic cookie, which is a packet of data a program receives and sends back unchanged, used by Unix programmers. Magic cookies were already used in computing when computer programmer Lou Montulli had the idea of using them in web communications in June 1994.

At that time he was an employee of Netscape Communications, which was developing an e-commerce application for MCI. Vint Cerf and John Klensin represented MCI in technical discussions with Netscape Communications. The development of the formal cookie specifications was already ongoing. In particular, the first discussions about a formal specification started in April 1995 on the www-talk mailing list. HTTP cookies were created to help websites maintain their state across multiple pages.

Where cookies are stored (browser’s local cookie file/storage)

Browser cookies are stored locally on your device’s hard drive within specific, isolated directories that are managed by the individual web browser.

Rather than being saved as plain (.txt) files scattered across your operating system, modern browsers secure and consolidate cookies inside encrypted SQLite database files embedded within your user profile directory.

The exact storage behaviour depends on your choice of web browser and operating system:

Physical File Paths by Browser (Windows & macOS)

• Google Chrome & Chromium-based Browsers (Edge, Brave, Opera)
  • Windows: %LocalAppData%\Google\Chrome\User Data\Default\Network\ (Look for the file named Cookies)
  • macOS: ~/Library/Application Support/Google/Chrome/Default/Network/
  • Note: Chrome encrypts the values inside this SQLite database file using OS-level credentials (like Windows DPAPI or macOS Keychain) to prevent unauthorised local access.
• Mozilla Firefox
  • Windows: %AppData%\Roaming\Mozilla\Firefox\Profiles\[profile_name]\ (Look for the file named cookies.sqlite)
  • macOS: ~/Library/Application Support/Firefox/Profiles/[profile_name]/cookies.sqlite
• Apple Safari
  • macOS: ~/Library/Cookies/ (Look for the file named Cookies.binarycookies)

What Is a Cookie for a Computer or Device?

What is a cookie for a device? A cookie for a computer or device is also known as an HTTP cookie — a small text file containing a piece of data that a website saves on your device through your web browser.

This helps the server to recognise the specific user via a unique identifier. However, cookies are tied to the specific web browser on a specific device, not to a device or an individual. Suppose you are switching from Chrome to Safari on the same device, or you move from your phone to your desktop; then cookies won’t follow you. In fact, each browser maintains its isolated jar for the cookies. 

However, cookies are not malware; they are harmless text files just containing data, not an executable program. They can’t harm your device with viruses or steal sensitive information. Still, some people fear them, which is not completely wrong; in fact, cookies are not malicious software, but they still carry privacy issues.

Types of Website Cookies

There are several different types of website cookies, depending upon how long they will last and who created them. Some of them help to recognise users, while other cookies store your preferences and track activity for future analytics.

Here are some different types of website cookies:

• Session cookies —  are temporary cookies that disappear when the browser closes.
• Persistent cookies — cookies that stay on the device for a set period.
• First-party cookies — set by the website the user is visiting.
• Third-party cookies — set by another domain, often used for ads or tracking.
• Authentication cookies — help manage the user session. They ensure that sensitive information is delivered to the authorised user.
• Zombie cookies — a type of persistent tracking data that recreates itself after being deleted by the user.

Difference between session cookies and persistent cookies:

Feature	Session Cookies	Persistent Cookies
Lifespan	Erased when the browser is closed.	Remain on the user’s device until they expire or are manually deleted.
Purpose	Remember user actions and preferences during a browsing session.	Remember user preferences and login information across multiple sessions.
Performance Improvement	Enhance website performance by reducing server requests.	Aid website performance optimization by reducing server requests.
Storage Space	Do not occupy much storage space.	May occupy storage space over time.
Privacy Concerns	Can potentially track users, leading to privacy concerns.	Often used for targeted advertising and tracking, potentially raising privacy concerns.

When websites are built or updated, developers may also consider whether to use a custom website or website builder based on the project’s requirements. 

Cookies Enabling — What Happens When You Allow or Block Them

Some cookies can be an optional part of your internet experience; for example, you can limit what cookies end up on your computer or mobile device. Today, when you visit a website, you are given the option to enable cookies or not. However, they are commonly used on every website nowadays.

If you enable cookies and allow them, it can streamline your web-surfing experience. Here’s how enabling cookies works:

• Find the cookie section — typically under Settings Privacy.
• Click the boxes to allow cookies. Sometimes the option says, allow “local” data.
• If you don’t want cookies, you can simply uncheck these boxes.

On the other hand, when someone rejects all the cookies or doesn’t accept them, they might face some issues. It may help you mitigate your privacy concerns. But enabling cookies can also reset all your information, like tracking or login details, on the web server, which might make it more difficult for different websites to track you and your preferences.

GDPR and CCPA consent banners exist because some data privacy laws require companies to be transparent with the user about tracking and give users control over their personal information.

Are Cookies Safe? Privacy Considerations

Cookies are generally safe because they can not harm your devices directly with malware or viruses. This doesn’t mean they are completely safe because some cookies potentially carry privacy risks and also depend on who created them and how they are used. 

Privacy considerations are as follows: 

User Tracking:

• Stored history: Cookies save the websites you visit on a regular basis and what content you are consuming.
• Behaviour profiles: Companies build a profile of a user’s habits over time by tracking their records to build influence.
• Targeted ads: Trackers use this data to show personalised ads. This influences our choices.

Third-Party Data Sharing:

• Outside access: External ad networks place cookies on multiple websites.
• Data pooling: These networks combine your activity across different pages.
• Sold information: Companies may share your data with other entities without direct consent.

As privacy and user experience become increasingly important, businesses may also review their sites through a broader website redesign process to improve functionality and user control.