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Website Cookies

Website cookies, formally known as HTTP cookies or browser cookies, are small pieces of data—specifically, text files—that a web server sends to a user's web browser. The browser stores this data and sends it back to the server with subsequent requests. This mechanism is fundamental for state management in the inherently stateless HTTP protocol.

Cookies possess attributes like an expiration date, domain, and path, which govern their persistence and scope. They are primarily used for three purposes:

  1. Session management (e.g., maintaining login status).
  2. Personalization (e.g., storing user preferences).
  3. Tracking (e.g., recording user behavior for analytics or targeted advertising).

They are set using the server's Set-Cookie HTTP response header and transmitted back to the server via the browser's Cookie HTTP request header.



Use Case

A classic and critical use case for website cookies is managing an E-commerce Shopping Cart prior to checkout.

  1. Initial Interaction: A user visits an online store. The server, upon the first request, generates a unique Session ID. It sets a session cookie (which is typically temporary, expiring when the browser closes) containing this Session ID using the Set-Cookie header.
  2. Adding Items: When the user adds an item to their cart, the browser automatically includes the Session ID cookie in the request. The server uses this ID to look up the user's session data stored on the server's side (often in a database or a specialized session store). It then associates the newly added item with this specific Session ID.
  3. Navigation and Return: As the user navigates other pages or even leaves and returns to the site within a short time (if a persistent cookie is also used), the cookie ensures the cart's contents persist. The browser transmits the Session ID, and the server retrieves the associated cart data, maintaining the state of the shopping experience despite the stateless nature of each individual HTTP request.
  4. Checkout: At checkout, the Session ID links the cart contents to the final purchase transaction.
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