What are the best language learning apps?

Duolingo is a language learning website in the same vein as sites like Lingvist.
It offers users the opportunity to study one or more languages including English, Spanish, Italian, French, and German.
The site requires you to return daily to accomplish objectives. It is not only a means of motivation, but also a way to gain the necessary experience over time to unlock the higher levels. These are of various styles consisting of both written and oral translations. It should be noted that the courses cover many subjects such as expressions, foods, animals, plurals, possessives, and questions of the country a language is primarily associated with. Duolingo tests your progress every eight lessons.

Memrise is a tool that gives you access to hundreds of thousands of courses on any topic on which you want to strengthen your knowledge or improve your level. Whatever you want to study, this application has more than 180 languages available, including Toki Pona (an artificial language) and Esperanto (almost extinct).
Among the themes present in Memrise in addition to languages, there are arts, sciences, mathematics, history, geography, and several others. All courses have been designed by professionals in each field and improved by other users who have studied them, ensuring you a quality learning experience adapted to your needs.

Babbel is an application that allows you to learn a language from your smartphone or tablet. Choose from English, Italian, Swedish, Russian, Turkish, and a dozen of other languages and embark on a progressive and effective learning program.
With short 15-minute sessions including complete and detailed lessons developed by linguists, Babbel adapts to all your needs, whether you are passionate about languages or just want to learn something new. To access the application you will need to subscribe to a membership, however you can try a first lesson for free.

Busuuu is a virtual community for language learning. It is a service that encourages social learning. Indeed, Internet users can chat via video conference with native speakers registered on the site in order to be "virtual immersed" in the language they're trying to learn. It is possible to learn English, German, Spanish, French, Italian, Portuguese, and other languages such as Arabic and Russian.
The platform offers more than 150 learning credits according to different themes. The language courses offered by Busuu are aimed at students of all levels.

Founded in 1999, Rosetta Stone is a method of learning foreign languages in the form of software.
The concept of this type of learning, called "immersion", is to learn a new language as we have learned our mother tongue. This method is quite popular in English-speaking countries but not well known in other ones.
Rosetta Stone boasts a track record of being deployed in more than 12,000 companies, 9,000 public organizations, and 22,000 educational institutions.

Mosalingua is an application for Android and iOS that allows rapid learning of many languages such as French, Italian, Spanish, Brazilian, Russian or German. It offers about ten levels of teaching and improvement and it is also equipped with a backup system that allows the user to keep his progress in his learning. This application has all the options to both refine understanding and improve oral skills.

HelloTalk is a mobile application published in 2012 and running on iOS and Android. It allows you to connect with people who speak a foreign language and want to learn yours. Communication with language partners is achieved through instant messaging or telephone calls (VoIP).
The app differs from other tools of its kind (WhatsApp, Viber, and others) thanks to features specially designed around learning foreign languages.
Other similar apps exist like Tandem and HiNative.