> Then how does WhatsApp run their service for free across multiple platforms?

FWIW, this is always a good question to ask yourself when considering using a service... they are getting paid for it one way or another.

Facebook mines the metadata to increase revenue received through advertising.

It’s not free, the end user just isn’t paying in monetary currency.

The last year it was independent, WhatsApp lost nearly $140M (on a much smaller userbase than it has today)

https://www.sec.gov/Archives/edgar/data/1326801/000132680114...