Cookies are small pieces of data stored on the user’s browser by a website. They are sent back to the server with each subsequent request, allowing the server to recognize the user and maintain stateful information across different pages and sessions.
Common Uses of Cookies:
- Session Management: Keeping users logged in as they navigate the site.
- Personalization: Storing user preferences and settings.
- Tracking and Analytics: Monitoring user behavior for insights and targeted advertising.
Types of Cookies
- Session Cookies:
- Duration: Temporary; deleted when the browser closes.
- Use Case: Maintaining session state (e.g., shopping cart contents).
- Persistent Cookies:
- Duration: Remain on the device for a set period or until manually deleted.
- Use Case: Remembering login details, language preferences.
- Secure Cookies:
- Attribute: Only transmitted over secure HTTPS connections.
- Use Case: Protecting sensitive information.
- HttpOnly Cookies:
- Attribute: Inaccessible via JavaScript, mitigating XSS attacks.
- Use Case: Storing session identifiers securely.
- Third-Party Cookies:
- Origin: Set by domains other than the one the user is visiting.
- Use Case: Advertising and tracking across multiple sites.
How Cookies Work
When a user visits a website, the server sends a cookie along with the HTTP response headers. The browser stores this cookie and includes it in subsequent requests to the same server. This exchange allows the server to identify returning users and maintain stateful interactions.
Example HTTP Headers:
- Setting a Cookie:
http Set-Cookie: sessionId=abc123; Path=/; HttpOnly; Secure
- Sending a Cookie:
http Cookie: sessionId=abc123