From SoloLearn Website
'' Learning on SoloLearn is completely free. Our apps are available on Android, iOS, and Web. We do have a premium subscription available called SoloLearn PRO. With a SoloLearn PRO subscription, you will have an ad-free experience with access to a more customized experience that includes setting learning goals and access to personalized activity insights. On the social front, you can see who’s viewed your profile and who’s learning nearby. We add new features regularly to improve the PRO experience further. ''