If you’re ever stuck wondering why Live HTTP Headers and Firebug are telling you your “Cookie:” request headers don’t match the “Set-Cookie:” response headers you’ve just been sent, here’s a couple of points and gotchas worth remembering:
- A cookie can only be overwritten (or deleted) by a subsequent cookie exactly matching the name, path and domain of the original cookie. Even though a cookie with domain “.example.org” set by www.example.org is perfectly valid, it will not overwrite a previous cookie of the same name which was set against “www.example.org”. Instead, both cookies will be stored, and on subsequent requests only one will be sent.
- If multiple cookies of the same name match a given request URI, one is chosen by the browser. The more specific the path, the higher the precedence. However precedence based on other attributes, including the domain, is unspecified, and may vary between browsers. This means that if you have set cookies of the same name against “.example.org” and “www.example.org”, you can’t be sure which one will be sent back.
- The HTTP state object is called a cookie
for no compelling reason
according to the preliminary specification from Netscape.
Frequently Asked Questions (FAQs) about Cookies
What are the different types of cookies and how do they function?
Cookies are small text files that websites store on your device. They come in different types, each serving a unique purpose. Session cookies are temporary and expire once you close your browser. They’re used to remember your activity on a website during a single visit. Persistent cookies, on the other hand, remain on your device until they’re manually deleted or until they reach their expiry date. They’re used to remember your preferences and actions across multiple visits. Third-party cookies are created by websites other than the one you’re visiting, usually for advertising and tracking purposes.
How can I manage cookies on my browser?
Most browsers offer settings that allow you to control how cookies are handled. You can choose to block all cookies, accept only first-party cookies, or delete cookies when you close your browser. These settings can usually be found in the ‘Privacy’ or ‘Advanced’ section of your browser’s settings menu. Remember, blocking all cookies might affect the functionality of some websites.
Can cookies pose a security risk?
While cookies themselves are not harmful, they can be used in ways that compromise your privacy. For instance, tracking cookies can monitor your online activity, while malicious cookies can be used for identity theft or other fraudulent activities. It’s important to regularly clear your cookies and to only allow cookies from trusted websites.
Why do some websites require cookies?
Cookies help websites provide a personalized experience. They can remember your login details, language preferences, and other settings, making your interactions with the website more convenient. Some websites might not function properly without cookies.
How do cookies affect website performance?
Cookies can enhance website performance by storing information locally on your device, reducing the need for the website to retrieve that information from the server each time you visit. This can result in faster load times and a smoother browsing experience.
What is the difference between first-party and third-party cookies?
First-party cookies are created by the website you’re visiting, while third-party cookies are created by other websites. Third-party cookies are often used for advertising and tracking purposes, and are generally considered less privacy-friendly than first-party cookies.
Can I choose which cookies to accept?
Yes, most browsers allow you to choose which types of cookies to accept. You can usually choose to accept all cookies, block all cookies, or accept only first-party cookies. Some browsers also offer the option to block third-party cookies.
How do cookies relate to my privacy?
Cookies can store a wide range of information, including personal details like your name and email address. While this can enhance your browsing experience by allowing websites to remember your preferences, it can also pose a privacy risk if this information is misused.
What are supercookies and zombie cookies?
Supercookies and zombie cookies are advanced types of cookies that are harder to delete and can track your online activity more persistently. Supercookies are stored outside the regular cookie storage area and can track your activity across all browsers on your device. Zombie cookies are automatically recreated after being deleted, making them difficult to permanently remove.
How can I protect myself from malicious cookies?
Regularly clearing your cookies, blocking third-party cookies, and only allowing cookies from trusted websites can help protect you from malicious cookies. Additionally, using a reputable antivirus program can help detect and remove malicious cookies.
Paul AnnesleyPaul is a Rails and PHP developer in the SitePoint group of companies.
