Cookies Basics
1. Introduction
Cookies are small pieces of data stored on the user's device by the web browser while browsing a website. They are commonly used to remember information about users, such as login credentials and site preferences.
2. What are Cookies?
Cookies are key-value pairs sent from the server to the client and stored on the client's device. They are included in the HTTP headers and can persist across sessions, allowing for stateful interactions.
3. How Cookies Work
When a client makes a request to a server, the server can send cookies in the HTTP response headers. The browser then stores these cookies and sends them back to the server in subsequent requests.
4. Cookie Attributes
Cookies can have several attributes that determine their behavior:
- Name: The name of the cookie.
- Value: The value of the cookie.
- Domain: The domain for which the cookie is valid.
- Path: The URL path for which the cookie is valid.
- Expires: The expiration date of the cookie.
- Secure: If true, the cookie will only be sent over HTTPS.
- HttpOnly: If true, the cookie cannot be accessed via JavaScript.
5. Best Practices
When using cookies, consider the following best practices:
- Use Secure and HttpOnly attributes to enhance security.
- Limit the size of cookies to avoid performance issues.
- Set appropriate expiration dates for cookies.
- Only store essential information in cookies.
- Regularly review and clear outdated cookies.
6. FAQ
What is the maximum size of a cookie?
The maximum size of a cookie is typically 4096 bytes. Browsers may have different limits, but it's a good practice to keep cookies smaller than this.
Can cookies be shared between different domains?
No, cookies are domain-specific. A cookie set by one domain cannot be accessed by another domain.
How can I delete a cookie?
You can delete a cookie by setting its expiration date to a date in the past. Example:
document.cookie = "myCookie=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/;";