WhatsApp Messenger from Facebook is a freeware, cross-platform messaging and Voice over IP (VoIP) service owned by Facebook.^[41] It allows users to send text messages and voice messages,^[42] make voice and video calls, and share images, documents, user locations, and other media.^[43][44] WhatsApp's client application runs on mobile devices but is also accessible from desktop computers, as long as the user's mobile device remains connected to the Internet while they use the desktop app.^[45] The service requires users to provide a standard cellular mobile number for registering with the service.^[46] In January 2018, WhatsApp released a standalone business app targeted at small business owners, called WhatsApp Business, to allow companies to communicate with customers who use the standard WhatsApp client.^[47][48]

The client application was created by WhatsApp Inc. of Mountain View, California, which was acquired by Facebook in February 2014 for approximately US$ 19.3 billion.^[49] Cite error: A tag is missing the closing (see the help page). ^[50] making it the world's most popular messaging application at the time.^[50][51] It has become the primary means of communication in multiple countries, including Brazil, India, Pakistan and large parts of Europe, including the United Kingdom and France.^[50]

WhatsApp was founded in 2009 by Brian Acton and Jan Koum, former employees of Yahoo!. After leaving Yahoo! in September 2007, they took some time off in South America.^[8] At one point, they applied for jobs at Facebook but were rejected.^[8]

In January 2009, after purchasing an iPhone and realizing the potential of the app industry on the App Store, Koum and Acton began visiting Koum's friend Alex Fishman in West San Jose to discuss a new type of messaging app that would "[show] statuses next to individual names of the people". They realized that to take the idea further, they'd need an iPhone developer. Fishman visited RentACoder.com, found Russian developer Igor Solomennikov, and introduced him to Koum.

Koum named the app WhatsApp to sound like "what's up".

On February 24, 2009, he incorporated WhatsApp Inc. in California.

However, when early versions of WhatsApp kept crashing, Koum considered giving up and looking for a new job. Acton encouraged him to wait for a "few more months".^[52]

In June 2009, Apple launched push notifications, allowing users to be pinged when they were not using an app. Koum changed WhatsApp so that when a user's status is changed, everyone in the user's network would be notified.^[8] WhatsApp 2.0 was released with a messaging component and the number of active users suddenly increased to 250,000. Although Acton was managing another startup, he decided to join the company.^[8] In October 2009, Acton persuaded five former friends at Yahoo! to invest $250,000 in seed funding, and Acton became a co-founder and was given a stake. He officially joined WhatsApp on November 1.^[8] After months at beta stage, the application launched in November 2009, exclusively on the App Store for the iPhone. Koum then hired a friend in Los Angeles, Chris Peiffer, to develop a BlackBerry version, which arrived two months later.^[8]

To cover the primary cost of sending verification texts to users, WhatsApp was changed from a free service to a paid one.

In December 2009, the ability to send photos was added to the iPhone version.

By early 2011, WhatsApp was one of the top 20 apps at Apple's U.S.

App Store.^[8]

In April 2011, Sequoia Capital invested about $8 million for more than 15% of the company, after months of negotiation with Sequoia partner Jim Goetz.^[53][54][55]

By February 2013, WhatsApp had about 200 million active users and 50 staff members.

Sequoia invested another $50 million, and WhatsApp was valued at $1.5 billion.^[8]

In a December 2013 blog post, WhatsApp claimed that 400 million active users used the service each month.^[56]

On February 19, 2014, months after a venture capital financing round at a $1.5 billion valuation,^[57] Facebook announced it was acquiring WhatsApp for US$19 billion, its largest acquisition to date.^[58] At the time, it was the largest acquisition of a venture-backed company in history.^[49] Sequoia Capital received an approximate 5000% return on its initial investment.^[59] Facebook, which was advised by Allen & Co, paid $4 billion in cash, $12 billion in Facebook shares, and (advised by Morgan Stanley) an additional $3 billion in restricted stock units granted to WhatsApp's founders Koum and Acton.^[60] Employee stock was scheduled to vest over four years subsequent to closing.^[58] Days after the announcement, WhatsApp users experienced a loss of service, leading to anger across social media.^[61]

The acquisition caused a considerable number of users to try and/or move to other message services.

Telegram claimed that it acquired 8 million new users;^[62] and Line, 2 million.^[63]

At a keynote presentation at the Mobile World Congress in Barcelona in February 2014, Facebook CEO Mark Zuckerberg said that Facebook's acquisition of WhatsApp was closely related to the Internet.org vision.^[64][65] A TechCrunch

Just three days after announcing the Facebook purchase, Koum said they were working to introduce voice calls.

He also said that new mobile phones would be sold in Germany with the WhatsApp brand, and that their ultimate goal was to be on all smartphones.^[66]

In August 2014, WhatsApp was the most globally popular messaging app, with more than 600 million users.^[67] By early January 2015, WhatsApp had 700 million monthly users and over 30 billion messages every day.^[68] In April 2015, Forbes predicted that between 2012 and 2018, the telecommunications industry would lose $386 billion because of OTT services like WhatsApp and Skype.^[69] That month, WhatsApp had over 800 million users.^[70][71] By September 2015, it had grown to 900 million;^[72] and by February 2016, one billion.^[73]

In November 30, 2015, the Android WhatsApp client made links to another message service, Telegram, unclickable and uncopyable.^[74][75][76] Multiple sources confirmed that it was intentional, not a bug,^[76] and that it had been implemented when the Android source code that recognized Telegram URLs had been identified.^[76] (The word "telegram" appeared in WhatsApp's code.^[76]) Some considered it an anti-competitive measure,^[74][75][76] but WhatsApp offered no explanation.

In response to the 2014 Facebook acquisition, Slate columnist Matthew Yglesias questioned whether the company's business model of charging users $1 a year was viable in the U.S.. It had prospered by exploiting a "loophole" in mobile phone carriers' pricing. "Mobile phone operators aren't really selling consumers some voice service, some data service, and some SMS service", he explained. "They are selling access to the network. The different pricing schemes they come up with are just different ways of trying to maximize the value they extract from consumers."^[77] As part of that, carriers sold SMS separately. This made it easy for WhatsApp to find a way to replicate SMS using data, then sell that service to mobile customers for $1 a year. "But if WhatsApp gets big enough, then carrier strategy is going to change", he predicted. "You stop selling separate SMS plans and just have a take-it-or-leave-it overall package. And then suddenly WhatsApp isn't doing anything."^[77] The situation may have been different in countries other than the United States.

On January 18, 2016, WhatsApp's co-founder Jan Koum announced that it would no longer charge users a $1 annual subscription fee, in an effort to remove a barrier faced by users without credit cards.^[78][31] He also said that the app would not display any third-party ads, and that it would have new features such as the ability to communicate with businesses.^[73][80]

By June 2016, the company's blog reported more than 100 million voice calls per day were being placed on WhatsApp.^[81]

On November 10, 2016, WhatsApp launched a beta version of two-step verification for Android users, which allowed them to use their email addresses for further protection.^[82] Also in November 2016, Facebook ceased collecting WhatsApp data for advertising in Europe.^[83]

On February 24, 2017, (WhatsApp's 8th birthday), WhatsApp launched a new Status feature similar to Snapchat and Facebook stories.^[84]

On May 18, 2017, it was reported that the European Commission would fine Facebook €110 million for "misleading" it during the 2014 takeover of WhatsApp. The Commission alleged that in 2014, when Facebook acquired the messaging app, it "falsely claimed it was technically impossible to automatically combine user information from Facebook and WhatsApp." However, in the summer of 2016, WhatsApp had begun sharing user information with its parent company, allowing information such as phone numbers to be used for targeted Facebook advertisements. Facebook acknowledged the breach, but said the errors in their 2014 filings were "not intentional."^[83]

In September 2017, WhatsApp's co-founder Brian Acton left the company to start a nonprofit group,^[85] later revealed as the Signal Foundation, which now develops the WhatsApp competitor Signal.^[86] WhatsApp also announced a forthcoming business platform to enable companies to provide customer service at scale,^[87] and airlines KLM and Aeroméxico announced their participation in the testing.^{[88][89][90][91]} Both airlines previously launched customer services on the Facebook Messenger platform.

In January 2018, WhatsApp launched WhatsApp Business for small business use.^[92]

In April 2018, WhatsApp co-founder and CEO Jan Koum announced he would be leaving the company.^[93] Facebook later announced that Koum's replacement would be Chris Daniels.^[6]

Later in September 2018, WhatsApp introduced group audio and video call features.^[94][95] In October, the "Swipe to Reply" option was added to the Android beta version, 16 months after it was introduced for iOS.^[96]

In May 2019, WhatsApp was hacked, and attackers installed spyware on an unknown number of smartphones.^[97] The hack, allegedly developed by Israeli surveillance technology firm NSO Group, injected malware onto WhatsApp users’ phones via a remote-exploit bug in the app's VoIP calling functions. A Wired report noted the attack was able to inject malware via calls to the targeted phone, even if the user didn't answer the call.^[7]

Until 2017, WhatsApp was for individual use between two smartphones.

This enabled businesses to communicate with customers,^[99] but not at scale (e.g. in a contact center environment). In September 2017 WhatsApp confirmed rumors^[100][101] that they were building and testing two new tools for businesses:^[91]

After months at beta stage, the official first release of WhatsApp launched in November 2009, exclusively at the App Store for iPhone.

In January 2010, support for BlackBerry smartphones was added; and subsequently for Symbian OS in May 2010, and for Android OS in August 2010. In August 2011, a beta for Nokia's non-smartphone OS Series 40 was added. A month later, support for Windows Phone was added, followed by BlackBerry 10 in March 2013.^[104] In April 2015, support for Samsung's Tizen OS was added.^[105] Unofficial ports, Wazapp and Yappari, have also been released for the MeeGo-based Nokia N9^[106] and the Maemo-based Nokia N900, respectively.^[107]

The oldest device capable of running WhatsApp was the Symbian-based Nokia N95 released in March 2007. (As of June 2017, WhatsApp is no longer compatible with it.)

In August 2014, WhatsApp released an Android update, adding support for Android Wear smartwatches.^[108]

In 2014, an unofficial open source plug-in, whatsapp-purple, was released for Pidgin, implementing its XMPP and making it possible to use WhatsApp on PCs running Microsoft Windows and Linux.^[109] WhatsApp responded by blocking phone numbers that used the plug-in.

On January 21, 2015, WhatsApp launched WhatsApp Web, a browser-based web client that could be used by syncing with a mobile device's connection.^[110]

On February 26, 2016, WhatsApp announced they would cease support for BlackBerry (including BlackBerry 10), Series 40, and Symbian S60, as well as older versions of Android (2.2), Windows Phone (7.0), and iOS (6), by the end of 2016.^[111] BlackBerry, Series 40, and Symbian support was then extended to June 30, 2017.^[112] In June 2017, support for BlackBerry and Series 40 was once again extended until the end of 2017, while Symbian was dropped.^[113]

Support for BlackBerry and older (version 8.0) Windows Phone and older (version 6) iOS devices was dropped on January 1, 2018, but was extended to December 2018 for Nokia Series 40.^[114] In July 2018, it was announced that WhatsApp would soon be available for KaiOS feature phones.^[115][116]

WhatsApp was officially made available for PCs through a web client, under the name WhatsApp Web, in late January 2015 through an announcement made by Koum on his Facebook page: "Our web client is simply an extension of your phone: the web browser mirrors conversations and messages from your mobile device—this means all of your messages still live on your phone". The WhatsApp user's handset must still be connected to the Internet for the browser application to function. All major desktop browsers are supported except for Internet Explorer. WhatsApp Web's user interface is based on the default Android one.

As of January 21, 2015, the desktop version was only available to Android, BlackBerry, and Windows Phone users.

Later on, it also added support for iOS, Nokia Series 40, and Nokia S60 (Symbian).^[117][118]

An unofficial derivative called WhatsAppTime has been developed, which is a standard Win32 application for PCs and supports notifications through the Windows notification area.^[119]

There are similar solutions for macOS, such as the open-source ChitChat.^{[120][121][122]}

On May 10, 2016, the messaging service was introduced for both Microsoft Windows and macOS operating systems. WhatsApp currently does not allow audio or video calling from desktop operating systems. Similar to the WhatsApp Web format, the app, which will be synced with a user's mobile device, is available for download on the website. It supports OS versions of Windows 8 and OS X 10.9 and higher.^[123][124]

WhatsApp uses a customized version of the open standard Extensible Messaging and Presence Protocol (XMPP).^[125] Upon installation, it creates a user account using one's phone number as the username (Jabber ID: [phone number]@s.whatsapp.net).

WhatsApp software automatically compares all the phone numbers from the device's address book with its central database of WhatsApp users to automatically add contacts to the user's WhatsApp contact list.

Previously the Android and Nokia Series 40 versions used an MD5-hashed, reversed-version of the phone's IMEI as password,^[126] while the iOS version used the phone's Wi-Fi MAC address instead of IMEI.^[127][128] A 2012 update now generates a random password on the server side.^[129]

Some Dual SIM devices may not be compatible with WhatsApp, though there are some workarounds for this.^[130]

In February 2015, WhatsApp introduced a voice calling feature; this helped WhatsApp to attract a completely different segment of the user population.^[131][132] On November 14, 2016, Whatsapp added video calling feature for users across Android, iPhone, and Windows Phone devices.^[133][134]

On November 2017, Whatsapp released a new feature that would let its users delete messages sent by mistake within a time frame of 7 minutes.^[135]

Multimedia messages are sent by uploading the image, audio or video to be sent to an HTTP server and then sending a link to the content along with its Base64 encoded thumbnail (if applicable).^[136]

WhatsApp follows a "store and forward" mechanism for exchanging messages between two users. When a user sends a message, it first travels to the WhatsApp server where it is stored. Then the server repeatedly requests the receiver acknowledge receipt of the message. As soon as the message is acknowledged, the server drops the message; it is no longer available in the database of the server. The WhatsApp server keeps the message only for 30 days in its database when it is not delivered (when the receiver is not active on WhatsApp for 30 days).^[137]

On November 18, 2014, Open Whisper Systems announced a partnership with WhatsApp to provide end-to-end encryption by incorporating the encryption protocol used in Signal into each WhatsApp client platform.^[138] Open Whisper Systems said that they had already incorporated the protocol into the latest WhatsApp client for Android, and that support for other clients, group/media messages, and key verification would be coming soon after.^[139] WhatsApp confirmed the partnership to reporters, but there was no announcement or documentation about the encryption feature on the official website, and further requests for comment were declined.^[140] In April 2015, German magazine Heise Security used ARP spoofing to confirm that the protocol had been implemented for Android-to-Android messages, and that WhatsApp messages from or to iPhones running iOS were still not end-to-end encrypted.^[141] They expressed the concern that regular WhatsApp users still could not tell the difference between end-to-end encrypted messages and regular messages.^[141] On April 5, 2016, WhatsApp and Open Whisper Systems announced that they had finished adding end-to-end encryption to "every form of communication" on WhatsApp, and that users could now verify each other's keys.^[35][142] Users were also given the option to enable a trust on first use mechanism in order to be notified if a correspondent's key changes.^[143] According to a white paper that was released along with the announcement, WhatsApp messages are encrypted with the Signal Protocol.^[144] WhatsApp calls are encrypted with SRTP, and all client-server communications are "layered within a separate encrypted channel".^[144] The Signal Protocol library used by WhatsApp is open-source and published under the GPLv3 license.^[144][145]

Cade Metz, writing in Wired, said, "WhatsApp, more than any company before it, has taken encryption to the masses."^[41]

WhatsApp Payments is a peer-to-peer money transfer feature that is currently only available in India. WhatsApp has received permission from the National Payments Corporation of India (NPCI) to enter into partnership with multiple banks in July 2017^[146] to allow users to make in-app payments and money transfers using the Unified Payments Interface (UPI).^[147] UPI enables account-to-account transfers from a mobile app without having any details of the beneficiary's bank.^[148] This feature is being pilot tested with over a million users since April 2019, however there hasn't been any update on the final roll out^[149].

On February 28, 2019, The New York Times reported that Facebook was “hoping to succeed where Bitcoin failed” by developing an in-house cryptocurrency that would be incorporated into WhatsApp. The project reportedly involves over 50 engineers under the direction of former PayPal president David Marcus. This 'Facebook coin' will reportedly be a stablecoin pegged to the value of a basket of different foreign currencies.^[150]

In July 2018, WhatsApp encouraged people to report fraudulent or violent messages after lynch mobs in India murdered innocent people after malicious WhatsApp messages falsely accused the victims of intending to abduct children.^[151]

In an investigation on the use of social media in politics, it was found that WhatsApp was being abused for the spread of fake news in the 2018 presidential elections in Brazil.^[152] Furthermore, it has been reported that US$3 million has been spent in illegal off-the-books contributions related to this practice.^[153]

Researchers and journalists have called on WhatsApp parent company, Facebook, to adopt measures similar to those adopted in India and restrict the spread of hoaxes and fake news.^[152]

WhatsApp was initially criticized for its lack of encryption, sending information as plaintext.^[154] Encryption was first added in May 2012.^{[155][156][157]}

In 2016, WhatsApp was widely praised for the addition of end-to-end encryption and earned a 6 out of 7 points on the Electronic Frontier Foundation's "Secure Messaging Scorecard."^[158] WhatsApp was criticized by security researchers and the Electronic Frontier Foundation for using backups that are not covered by end-to-end encryption and allow messages to be accessed by third-parties.^[159][160]

In May 2019, a security vulnerability in WhatsApp was found and fixed that allowed a remote person to install spyware by making a call which did not need to be answered.^[161]

In September 2019, WhatsApp was criticized for its implementation of a 'delete for everyone' feature.

iOS users can elect to save media to their camera roll automatically.

When a user deletes media for everyone, WhatsApp doesn't delete images saved in the iOS camera roll and so those users are able to keep the images.

WhatsApp released a statement saying that "the feature is working properly," and that images stored in the camera roll cannot be deleted due to Apple's security layers.^[162]

NHS

In 2018 it was reported that around 500,000 NHS staff used WhatsApp and other instant messaging systems at work and around 29,000 had faced disciplinary action for doing so. Higher usage was reported by frontline clinical staff to keep up with care needs, even though NHS trust policies do not permit their use.^[163]

Mods and Fake versions

In March 2019, WhatsApp released a guide for users that had installed unofficial modified versions of WhatsApp and warned against data loss in case users persisted in using the same as it considered banning such users.^[164]

In December 2015, it was reported that Islamic State terrorists had been using WhatsApp to plot the November 2015 Paris attacks.^[165] ISIS also uses WhatsApp to traffic sex slaves.^[166]

In March 2017, U.K.

Secretary of State Amber Rudd said encryption capabilities of messaging tools like WhatsApp are unacceptable, as news reported that Khalid Masood used the application several minutes before perpetrating the 2017 Westminster attack. Rudd publicly called for police and intelligence agencies to be given access to WhatsApp and other encrypted messaging services to prevent future terror attacks.^[167]

In April 2017, the perpetrator of the Stockholm attack reportedly used WhatsApp to exchange messages with an ISIS supporter shortly before and after the 2017 Stockholm attack. The messages involved discussing how to make an explosive device and a confession of the perpetration after the attack.^[168]

It has been asserted that WhatsApp is plagued by scams that invite hackers to spread malicious viruses or malware.^[169][170] In May 2016, some WhatsApp users were reported to have been tricked into downloading a third-party application called WhatsApp Gold, which was part of a scam that infected the users' phones with malware.^[171] A message that promises to allow access to their WhatsApp friends' conversations, or their contact lists, has become the most popular hit against anyone who uses the application in Brazil. Since December, 2016, more than 1.5 million people have clicked and lost money.^[172]

Another application called GB Whatsapp is considered malicious by cybersecurity firm Symantec because it usually performs some unauthorized operations on end-user devices.^[173]

In 2017, security researchers reported to The New York Times that the WhatsApp service had been completely blocked in China.^[174] WhatsApp is owned by Facebook, whose main social media service has been blocked in China since 2009.^[175]

On May 9, 2014, the government of Iran announced that it had proposed to block the access to WhatsApp service to Iranian residents. "The reason for this is the assumption of WhatsApp by the Facebook founder Mark Zuckerberg, who is an American Zionist," said Abdolsamad Khorramabadi, head of the country's Committee on Internet Crimes. Subsequently, Iranian president Hassan Rouhani issued an order to the Ministry of ICT to stop filtering WhatsApp.^[176][177]

Turkey temporarily banned WhatsApp in 2016, following the assassination of the Russian ambassador to Turkey.^[178]

On March 1, 2016, Diego Dzodan, Facebook's vice-president for Latin America was arrested in Brazil for not cooperating with an investigation in which WhatsApp conversations were requested.^[179] On March 2, 2016, at dawn the next day, Dzodan was released because the Court of Appeal held that the arrest was disproportionate and unreasonable.^[180]

On May 2, 2016, mobile providers in Brazil were ordered to block WhatsApp for 72 hours for the service's second failure to cooperate with criminal court orders.^[181][182] Once again, the block was lifted following an appeal, after nearly 24 hours.^[183]

WhatsApp, one of the most activated messaging apps along with other social media networks such as Facebook and Instagram were temporarily blocked, banned and had been unavailable for about two days (7–8 March 2018) in certain parts of the country to eradicate communal violence, especially the anti-Muslim riots.^[184] This was probably the first such instance where social media platforms had been banned in Sri Lanka. The ban was finally lifted on the 14th of March, 2018 around midnight time in Sri Lanka.^[185]

The government of Uganda banned WhatsApp and Facebook, along with other social media platforms, to enforce a tax on the use of social media.^[186] Users are to be charged 200 shilling per day to access these services according to the new law set by parliament.^[187]

WhatsApp handled ten billion messages per day in August 2012,^[188] growing from two billion in April 2012,^[189] and one billion the previous October.^[190] On June 13, 2013, WhatsApp announced that they had reached their new daily record by processing 27 billion messages.^[191] According to the Financial Times, WhatsApp "has done to SMS on mobile phones what Skype did to international calling on landlines."^[192]

As of April 22, 2014, WhatsApp had over 500 million monthly active users, 700 million photos and 100 million videos were being shared daily, and the messaging system was handling more than 10 billion messages each day.^[193][194]

On August 24, 2014, Koum announced on his Twitter account that WhatsApp had over 600 million active users worldwide. At that point WhatsApp was adding about 25 million new users every month, or 833,000 active users per day.^[67][195] With 65 million active users representing 10% of the total worldwide users, India has the largest number of consumers.^[196]

In May 2017, it was reported that WhatsApp users spend over 340 million minutes on video calls each day on the app.

This is the equivalent of roughly 646 years of video calls per day.^[197]

As of February 2017, WhatsApp had over 1.2 billion users globally,^[198] reaching 1.5 billion monthly active users by the end of 2017.^[199]

India is by far WhatsApp's largest market in terms of total number of users.

In May 2014, WhatsApp crossed 50 million monthly active users in India, which is also its largest country by the number of monthly active users,^[200] then 70 million in October 2014, making users in India 10% of WhatsApp's total user base.^[201] In February 2017, WhatsApp reached 200 million monthly active users in India.^[202]

Israel is one of WhatsApp's strongest markets in terms of ubiquitous usage. According to Globes, already by 2013 the application was installed on 92% of all smartphones, with 86% of users reporting daily use.^[203] WhatsApp's group chat feature is reportedly used by many Israeli families to stay in contact with each other.^[204]

WhatsApp competes with a number of messaging services.

Those, as of 2019, were services like iMessage (estimated 1.3 billion active users^[205]), WeChat (1 billion active users^[206]), Viber (260 million active users^[207]), Telegram (200 million users^[208]) and LINE (187 million active users^[209]). Telegram in particular was reported to get registration spikes during WhatsApp outages and controversies.^{[210][211][212]}

WhatsApp has increasingly drawn its innovation from others^[213] such as a Telegram-inspired web version^[214] and features for groups.^[215] In 2016, WhatsApp was accused of copying features from a then-unreleased version of iMessage.^[216]