There were optional in-app purchases and they have introduced Duolingo Plus recently - which enables users to download lessons for offline learning & removes ad

There were optional in-app purchases and they have introduced Duolingo Plus recently - which enables users to download lessons for offline learning & removes ads. It's Android only for now and the price is $10 month. [0] [0] https://www.duolingo.com/comment/22202238/Introducing-Duolingo-Plus https://www.duolingo.com/comment/22202238/Introducing-Duolin...