When it launched, WhatsApp was offered as a paid-for app. Users would pay an up-front fee to download it and messaging was then free. In 2013 the company made the app free but added a $1 per year (around £0.70) fee to use the service.WhatsApp was purchased by Facebook in 2014 and, in a blog written prior to the Facebook acquisition, Acton and Koum promised the app wouldn’t become “just another ad clear.

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However, in 2016 WhatsApp announced that it would no longer charge a fee for the service, leaving no clear way for the company to make money. Acton and Koum both quit the firm last year, after the news emerged that Facebook was planning to monetise the app by selling services to business and advertising.

Acton said he had to leave because Mark Zuckerberg’s rush to make money from the app was making him “unhappy”.