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Cloudflare, Inc.
Cloudflare logo.svg
FoundedJuly 2009; 9 years ago (2009-07)
  • Matthew Prince
  • Lee Holloway
  • Michelle Zatlyn
Key people
  • Matthew Prince (CEO)
  • Lee Holloway
  • Michelle Zatlyn
Alexa rankPositive decrease 1056 (February 2019)[1]

Cloudflare, Inc. is a U.S. company that provides content delivery network services, DDoS mitigation, Internet security and distributed domain name server services. Cloudflare's services sit between the visitor and the Cloudflare user's hosting provider, acting as a reverse proxy for websites. Cloudflare's headquarters are in San Francisco, California, with additional offices in London, Singapore, Champaign, Austin, Boston and Washington, D.C.[2][3]


Cloudflare was created in 2009 by Matthew Prince, Lee Holloway, and Michelle Zatlyn,[4][5] who had previously worked on Project Honey Pot.[5][6] Cloudflare was launched at the September 2010 TechCrunch Disrupt conference.[4][5] It received media attention in June 2011, after providing security to LulzSec's website.[4][7]

In June 2012, Cloudflare partnered with various web hosts, including HostPapa, to implement its "Railgun" technology.[8][9]

In February 2014, Cloudflare mitigated the largest-ever recorded DDoS attack at that time, which peaked at 400 Gbit/s against an undisclosed customer.[10] In November 2014, Cloudflare reported another massive DDoS attack with independent media sites being targeted at 500 Gbit/s.[11]

Funding rounds[edit]

In November 2009, Cloudflare raised $2.1 million in a Series A round from Pelion Venture Partners and Venrock.[12]

In July 2011, Cloudflare raised $20 million in a Series B round from New Enterprise Associates, Pelion Venture Partners, Venrock.[12][13][14]

In December 2012, Cloudflare raised $50 million in a Series C round from New Enterprise Associates, Pelion Venture Partners, Venrock, Union Square Ventures, and Greenspring Associates.[15][16][17]

In December 2014, Cloudflare raised $110 million in a Series D round led by Fidelity Investments, with participation from Google Capital, Microsoft, Qualcomm, and Baidu.[18]


In February 2014, it acquired StopTheHacker, which offers malware detection, automatic malware removal, and reputation and blacklist monitoring.[19][20] In December 2016, Cloudflare acquired Eager, with the view of upgrading Cloudflare's Apps platform to allow for drag-and-drop of installation of third-party apps onto Cloudflare-enabled sites.[21]


DDoS protection[edit]

For all customers Cloudflare offers an "I'm Under Attack" mode. Cloudflare claims this can mitigate advanced Layer 7 attacks by presenting a JavaScript computational challenge which must be completed by a user's browser before the user can access a website.[22]

Cloudflare defended SpamHaus from a DDoS attack that exceeded 300 Gbit/s. Akamai's chief architect stated that at the time it was "the largest publicly announced DDoS attack in the history of the Internet".[23][24] Cloudflare has also reportedly absorbed attacks that have peaked over 400Gbit/s from an NTP Reflection attack.[25]

Web application firewall[edit]

Cloudflare allows customers on paid plans to utilize a web application firewall service, by default; the firewall has the OWASP ModSecurity Core Rule Set alongside Cloudflare's own ruleset and rulesets for popular web applications.[26]

Authoritative DNS[edit]

Cloudflare offers free authoritative Domain Name System (DNS) service for all clients which are powered by an anycast network.[27] According to W3Cook Cloudflare's DNS service currently powers over 35% of managed DNS domains.[28] SolveDNS have found Cloudflare to consistently have one of the fastest DNS lookup speeds worldwide, with a reported lookup speed of 8.66ms in April 2016.[29]

Public DNS resolver[edit]

On April 1, 2018, Cloudflare announced a 'privacy-first' consumer DNS service, hosted at IP addresses and Alternatively, the service can be accessed via IPv6 at 2606:4700:4700::1111 and 2606:4700:4700::1001.[30] [31]

On November 11, 2018, Cloudflare announced a mobile version of their service for iOS and Android.[32]

Reverse proxy[edit]

A key functionality of Cloudflare is that they act as a reverse proxy for web traffic.

Cloudflare supports new web protocols, including SPDY and HTTP/2. In addition to this, Cloudflare offers support for HTTP/2 Server Push.[33] Cloudflare also supports proxying Websockets.

Content delivery network[edit]

Cloudflare's network has the highest number of connections to Internet exchange points of any network worldwide.[34] Cloudflare caches content to its edge locations to act as a content delivery network (CDN), all requests are then reverse proxied through Cloudflare with cached content served directly from Cloudflare.

Project Galileo[edit]

In 2014, Cloudflare introduced Project Galileo in response to cyber attacks launched against important, yet vulnerable targets, such as artistic groups, humanitarian organizations, and the voices of political dissent. Working with free speech, public interest, and civil society organizations, Cloudflare then extended its Enterprise-class DDoS protection and business-level performance benefits to ensure these websites stay online, without being violated.


Cloudflare has been vocal of their values, with CEO Matthew Prince stating:

One of the greatest strengths of the United States is a belief that speech, particularly political speech, is sacred. A website, of course, is nothing but speech ... A website is speech. It is not a bomb. There is no imminent danger it creates and no provider has an affirmative obligation to monitor and make determinations about the theoretically harmful nature of speech a site may contain.[35]

Cloudflare publishes a Transparency Report on a semiannual basis to show how often law enforcement agencies request data about its clients.[36]

Cloudflare hosts the controversial website, which bills itself as a free speech alternative to

Breaking with its long-standing policy of total content neutrality, Cloudflare withdrew access to its services by white supremacist web site The Daily Stormer on 16 August 2017, in the aftermath of the fatal vehicular attack at the Charlottesville rally four days earlier. This withdrew the website's protection against distributed denial of service attack, and soon thereafter attackers took down the website.[37] CEO Matthew Prince stated: "I woke up this morning in a bad mood and decided to kick them off the internet",[38] the tipping point in the decision being "that the team behind Daily Stormer made the claim that we were secretly supporters of their ideology."[39][40] Andrew Anglin, editor for The Daily Stormer, denied that his team made such a claim,[41] and the move to disconnect The Daily Stormer from Cloudflare services was criticised as 'dangerous' by Prince himself,[42][43] Anglin,[41] and the Electronic Frontier Foundation.[44]


Cloudflare provides DNS services to 12 million websites,[45] adding approximately 20,000 new customers every day.[46] 

Awards and recognition[edit]

Criticism and controversies[edit]

The hacker group UGNazi attacked Cloudflare partially via flaws in Google's authentication systems in June 2012, gaining administrative access to Cloudflare and using it to deface 4chan.[52][53] Cloudflare published in full the details of the hack. Following this, Google publicly announced they had patched the flaw in the Google Enterprise App account recovery process which allowed the hackers to bypass two-step verification.[54]

From September 2016 until February 2017, a major Cloudflare bug (nicknamed Cloudbleed) leaked sensitive data—including passwords and authentication tokens from customer websites, by sending extra data in response to web requests.[55] The leaks resulted from a buffer overflow, which occurred, according to analysis by Cloudflare, on approximately 1 in every 3,300,000 HTTP requests.[56][57]

In May 2017, ProPublica reported that Cloudflare as a matter of policy relays the names and email addresses of persons complaining about hate sites to the sites in question, which has led to the complainants being harassed. Cloudflare's general counsel defended the company's policies by saying it is "base constitutional law that people can face their accusers."[58] In response Cloudflare updated their abuse reporting process to provide greater control of whom to notify for the complaining party.[59]

In September 2017, free-speech advocates criticized Cloudflare for dropping the American neo-Nazi website The Daily Stormer as a customer, which made it difficult for The Daily Stormer to stay online. "Denying security service to one Nazi website seems fine now, but what if Cloudflare started suspending service for a political candidate that its chief executive didn't like?" wrote Yale Law School doctoral candidate Kate Klonick in a New York Times article entitled "The Terrifying Power of Internet Censors", noting "the scarcity of competitors".[60]

Criticism of total content neutrality[edit]

Cloudflare was ranked in the 7th rank among the top 50 Bad Hosts by HostExploit.[61] The service has been used by Rescator, a website that sells payment card data.[62][63][64]

Two of Islamic State of Iraq and the Levant's top three online chat forums are guarded by Cloudflare but U.S. law enforcement has not asked them to discontinue the service, and they have not chosen to do so themselves.[65]

An October 2015 report found that Cloudflare provisioned 40% of SSL certificates used by phishing sites with deceptive domain names resembling those of banks and payment processors.[66]

In November 2015, Anonymous discouraged the use of Cloudflare's services, following the ISIL attacks in Paris and the renewed accusation that it provides help to terrorists.[67] Cloudflare responded by calling their accusers "15-year-old kids in Guy Fawkes masks" and saying that whenever such concerns are raised they consult actual anti-terrorism experts and abide by the law.[68]

Criticism of spam support[edit]

Cloudflare is listed on Spamhaus for providing spam support services (pink contract). The current list of Spamhaus listings changes on a near daily basis as reported issues are addressed with the responsible website owner.[69][70]


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External links[edit]