Amazon Underground was an Android app offered by Amazon through which people could freely download and obtain in-app items that they otherwise had to pay money to purchase. Amazon used the catchphrase "Actually Free" to describe the policy, and affirmed that Amazon Underground was not a one-time or temporary offer but was here to stay. Participation by app developers in the program was voluntary. Amazon compensated app developers based on the time that users spent within the app, at a flat rate of $0.002 per user minute.
Amazon announced on April 28, 2017 that the program would cease accepting new apps on May 31, 2017 and would shut down completely in 2019.