Editing World Wide Web (section)

===Cookie===
{{main|HTTP cookie}}
An ''HTTP cookie'' (also called ''web cookie'', ''Internet cookie'', ''browser cookie'', or simply ''cookie'') is a small piece of data sent from a website and stored on the user's computer by the user's [[web browser]] while the user is browsing. Cookies were designed to be a reliable mechanism for websites to remember [[program state|stateful]] information (such as items added in the shopping cart in an online store) or to record the user's browsing activity (including clicking particular buttons, [[access control|logging in]], or recording which pages were visited in the past). They can also be used to remember arbitrary pieces of information that the user previously entered into form fields such as names, addresses, passwords, and credit card numbers.

Cookies perform essential functions in the modern web. Perhaps most importantly, ''authentication cookies'' are the most common method used by web servers to know whether the user is logged in or not, and which account they are logged in with. Without such a mechanism, the site would not know whether to send a page containing sensitive information or require the user to authenticate themselves by logging in. The security of an authentication cookie generally depends on the security of the issuing website and the user's [[comparison of web browsers#Vulnerabilities|web browser]], and on whether the cookie data is encrypted. Security vulnerabilities may allow a cookie's data to be read by a [[hacker (computer security)|hacker]], used to gain access to user data, or used to gain access (with the user's credentials) to the website to which the cookie belongs (see [[cross-site scripting]] and [[cross-site request forgery]] for examples).<ref>{{cite web |url=http://news.cnet.com/8301-10789_3-9918582-57.html |first=Robert |last=Vamosi |title=Gmail cookie stolen via Google Spreadsheets |website=News.cnet.com |date=14 April 2008 |access-date=19 October 2017 |archive-date=9 December 2013 |archive-url=https://web.archive.org/web/20131209210402/http://news.cnet.com/8301-10789_3-9918582-57.html |url-status=dead }}</ref>

Tracking cookies, and especially third-party tracking cookies, are commonly used as ways to compile long-term records of individuals' browsing histories {{En dash}} a potential [[Internet privacy#HTTP cookies|privacy concern]] that prompted European<ref>{{cite web |title=What about the "EU Cookie Directive"? |url=http://webcookies.org/faq/#Directive |year=2013 |publisher=WebCookies.org |access-date=19 October 2017 |archive-date=11 October 2017 |archive-url=https://web.archive.org/web/20171011095259/https://webcookies.org/faq/#Directive |url-status=dead }}</ref> and U.S. lawmakers to take action in 2011.<ref name="eulaw">{{cite news |url=https://www.bbc.co.uk/news/technology-12668552 |work=BBC |title=New net rules set to make cookies crumble |date=8 March 2011 |access-date=18 February 2019 |archive-date=10 August 2018 |archive-url=https://web.archive.org/web/20180810220427/https://www.bbc.co.uk/news/technology-12668552 |url-status=live }}</ref><ref>{{cite web |url=http://adage.com/article/digital/sen-rockefeller-ready-a-real-track-bill/227426/ |work=Adage.com |title=Sen. Rockefeller: Get Ready for a Real Do-Not-Track Bill for Online Advertising |date=6 May 2011 |access-date=18 February 2019 |archive-date=24 August 2011 |archive-url=https://web.archive.org/web/20110824225528/http://adage.com/article/digital/sen-rockefeller-ready-a-real-track-bill/227426/ |url-status=live }}</ref> European law requires that all websites targeting [[European Union]] member states gain "informed consent" from users before storing non-essential cookies on their device.

Google [[Project Zero (Google)|Project Zero]] researcher Jann Horn describes ways cookies can be read by [[Man-in-the-middle attack|intermediaries]], like [[Wi-Fi]] hotspot providers. When in such circumstances, he recommends using the browser in [[private browsing]] mode (widely known as [[Incognito mode]] in Google Chrome).<ref>[https://thejh.net/written-stuff/want-to-use-my-wifi? Want to use my wifi?] {{Webarchive|url=https://web.archive.org/web/20180104070103/https://thejh.net/written-stuff/want-to-use-my-wifi |date=4 January 2018 }}, Jann Horn accessed 5 January 2018.</ref>