[3] Yan Borysovych Koum was born in Kyiv, then in the Ukrainian SSR, on February 24, 1976 into a Jewish family.

He enrolled at San Jose State University and simultaneously worked at Ernst & Young as a security tester.

[6] He also joined w00w00, a computer security think tank started in 1996, where he met future Napster creators Shawn Fanning and Jordan Ritter.

[6] WhatsApp was initially unpopular, but its fortunes began to turn after Apple added push notification ability to apps in June 2009.

[6] The app gained a large user base, and Koum convinced Acton, then unemployed, to join the company.

[17] However, several months later it was discovered that he was still formally employed by Facebook, earning a reported $450 million in stock from the company through a method called "rest and vest".

[24] Koum has made donations to many Israeli causes: $600,000 to the Maccabee Task Force, $6 million to Friends of Ir David, and $175,000 to Central Fund of Israel.

[24] During the 2024 U.S. election campaign, Koum was one of the leading donors to the United Democracy Project, a Super PAC affiliated with the pro-Israel group AIPAC.

[31] In February 1996, a San Jose court issued a restraining order against Koum after his ex-girlfriend accused him of verbal and physical threats.

In November 2023, Koum acquired Château de la Garoupe in Cap d'Antibes on the French Riviera, previously owned by the Russian oligarch Boris Berezovsky, for about 65 million euros.