HTTP cookie

HTTP cookie (also called web cookie, Internet cookie, browser cookie, or simply cookie) is a small block of <a href="/facts/Data_(computing)/cPjfFHph">data</a> created by a <a href="/facts/Web_server/A4GS6thA">web server</a> while a <a href="/facts/User_(computing)/zQRzG0KG">user</a> is <a href="/facts/Browsing/cXxs5jsD">browsing</a> a <a href="/facts/Website/SAsjJnca">website</a> and placed on the user's computer or other device by the user's <a href="/facts/Web_browser/2pfyymLs">web browser</a>. Cookies are placed on the device used to access a website, and more than one cookie may be placed on a user's device during a session.
Cookies serve useful and sometimes essential functions on the <a href="/facts/World_Wide_Web/wvnTrWFq">web</a>. They enable web servers to store <a href="/facts/Program_state/4Yu8xXHS">stateful</a> information (such as items added in the shopping cart in an <a href="/facts/Online_shopping/KaWoKPBI">online store</a>) on the user's device or to track the user's browsing activity (including clicking particular buttons, <a href="/facts/Access_control/08zE5Pz8">logging in</a>, or recording which <a href="/facts/Web_browsing_history/Ted9Hbx4">pages were visited in the past</a>). They can also be used to save information that the user previously entered into <a href="/facts/Form_(HTML)/9Ivp2peo">form fields</a>, such as names, addresses, <a href="/facts/Password/WEoul230">passwords</a>, and <a href="/facts/Payment_card_number/g9C3edYe">payment card numbers</a> for subsequent use.
Authentication cookies are commonly used by web servers to <a href="/facts/Authentication/64y4S69b">authenticate</a> that a user is logged in, and with which <a href="/facts/Account_verification/vMAgNQ2m">account</a> they are logged in. Without the cookie, users would need to authenticate themselves by logging in on each page containing sensitive information that they wish to access. The security of an authentication cookie generally depends on the security of the issuing website and the user's web browser, and on whether the cookie data is <a href="/facts/Encryption/16q29Fdv">encrypted</a>. <a href="/facts/Vulnerability_(computing)/jg0Gr71M">Security vulnerabilities</a> may allow a cookie's data to be read by an <a href="/facts/Security_hacker/4bAJ9F1A">attacker</a>, used to gain access to <a href="/facts/Personal_data/384PbBg5">user data</a>, or used to gain access (with the user's credentials) to the website to which the cookie belongs (see <a href="/facts/Cross-site_scripting/dhtusKKm">cross-site scripting</a> and <a href="/facts/Cross-site_request_forgery/RN7XuvsW">cross-site request forgery</a> for examples).
Tracking cookies, and especially third-party tracking cookies, are commonly used as ways to compile long-term records of individuals' <a href="/facts/Web_browsing_history/Ted9Hbx4">browsing histories</a> — a potential <a href="/facts/Internet_privacy/Fdnjfnds">privacy concern</a> that prompted European and U.S. lawmakers to take action in 2011. European law requires that all websites targeting <a href="/facts/European_Union/6GYcR8qM">European Union</a> member states gain "<a href="/facts/Informed_consent/V1vL4QSj">informed consent</a>" from users before storing non-essential cookies on their device.

HTTP cookie open-in-new

HTTP cookie