The development came as a major surprise, given how desperately Facebook had been trying to monetize the messaging service, and left questions over the possibility of ads appearing in WhatsApp in the future.
Now, thanks to a new report, we have some answers around that.
Essentially, the company will move ahead with the project once it is done unifying the underlying infrastructure of the messaging service with Facebook Messenger and Instagram DMs - another ambitious project the social network announced last year.
Phone numbers to be used for displaying ads
While Facebook had already announced that it would show ads in the Status section of WhatsApp, much like Instagram ads, there was little-to-no information around how it would determine what ads to show on the end-to-end encrypted service.
The Information report now sheds light on this, noting that the company would use phone numbers to match WhatsApp and Facebook accounts and target adverts accordingly.
Matching would be easier post unification
Currently, WhatsApp, Messenger, and Instagram DMs operate as separate products.
But, once their underlying infrastructure is unified, it would be easier for the social network to use WhatsApp phone numbers and match them with those on other platforms.
This would allow the company to find users active on both WhatsApp and Facebook, and use their Facebook activity to show ads on WhatsApp.
Facebook employees are already raising concerns over this
The number-matching plan has already concerned Facebook employees who say that the move could force users to delete their Facebook accounts.
There are also concerns that many privacy watchdogs and regulators would not like the idea of WhatsApp numbers being matched with those on Facebook, a platform that has been marred by several privacy-related debacles and is subject to multiple anti-trust investigations.
No word on roll-out timeline yet
The report does not mention a timeline for the roll-out of ads but as the plan is to make the move after the unification of the three services, you should not expect adverts on your WhatsApp anytime soon.
Facebook has already said that the merger between the three platforms would take years and "ads in Status remains a long-term opportunity for WhatsApp."