WhatsApp is ditching subscription fees to make the service completely free to use, no matter how long you use it for.

Until now, the messaging app has been free for the first year of use but then charged a fee of 99 US cents for each extra year. That has been scrapped in favour of an uncharged model.

It's not clear how the Facebook-owned company will be financed in the future, with other business models being explored. WhatsApp however claims that every effort will be made to avoid spam or unwanted advertising.

"Naturally, people might wonder how we plan to keep WhatsApp running without subscription fees and if today’s announcement means we’re introducing third-party ads. The answer is no," it said in a blog post.

"Starting this year, we will test tools that allow you to use WhatsApp to communicate with businesses and organisations that you want to hear from. That could mean communicating with your bank about whether a recent transaction was fraudulent, or with an airline about a delayed flight.

"We all get these messages elsewhere today – through text messages and phone calls – so we want to test new tools to make this easier to do on WhatsApp, while still giving you an experience without third-party ads and spam."

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Facebook Messenger uses similar systems to make money currently.

WhatsApp founder Jan Koum said that the subscription model had to be discarded because "it really doesn't work that well".