How do cookies work, and what are their uses and privacy risks?

Cookies are data stored in a browser and may contain identifiers and preference information. When a user returns to a website, the browser sends the cookies back to the server, helping the site remember login status, shopping carts, and personal settings. Cookies can also support traffic analysis and ad targeting. Privacy risks depend on how the data is used and how widely it is shared: third-party cookies, in particular, can be used to link activity across websites and build user profiles. Understanding cookies means looking not only at their convenience, but also at who uses the data and for what purposes.

How do websites use cookies to remember visitors?

According to an introduction published by Welly in 2025, the basic process is as follows: a user visits a website, and the server sends the browser a cookie containing information such as an identifier. The browser stores it and sends it back on subsequent visits, allowing the website to recognize and maintain the user’s previous session state.

For example, a website can use cookies to remember language or region preferences so visitors do not have to select them each time. The key here is the mechanism for storing and returning information between the browser and the website, rather than treating every use as advertising tracking.

From logins to traffic analysis, what are cookies used for?

Cookies support both website functionality and marketing analysis, which should be understood separately:

• Maintaining login status: Helping websites remember that a user is logged in.
• Saving shopping carts: Retaining selected items to support the rest of the shopping process.
• Remembering preferences and recommending content: Saving language, region, or theme settings and supporting personalized content recommendations.
• Analyzing usage: Helping websites understand traffic and visitor behavior.

Thus, cookies may be used to keep shopping features working smoothly or to analyze browsing habits. When websites disclose their use of cookies, they should explain the specific purposes rather than simply stating that cookies “improve the experience.”

How do first-party and third-party cookies differ in terms of privacy?

First-party cookies are created by the website the user is visiting and are commonly used for that site’s preferences, logins, and shopping carts. Welly attributes their lower privacy risk to the data being used only within that website. This assessment should be understood in the context of that limited use, not as a guarantee that all first-party cookies are risk-free.

Third-party cookies are created by parties other than the website being visited, such as advertising networks or external tools. They can collect information about user behavior across multiple websites to build more comprehensive user profiles, which are then used for ad targeting. The privacy concern is not merely that a visit is remembered, but that records from multiple sites are linked and data is shared among multiple parties.

Websites should clearly disclose their use of cookies and offer users choices, while also paying attention to applicable data protection rules, such as the GDPR. For readers, distinguishing between preserving website functionality and tracking across sites is a starting point for understanding the privacy implications of cookies.