One of the downsides of the Google Play Store that many app developers will tell you is the lack of integration of promo codes to give away paid apps for FREE. That is soon to be a thing of the past, as Google has finally unveiled its plans for app promo codes for Google Play Store.
Developers will be able to create up to 500 one-time use codes for either the purchase of an app, or an in-app purchase, with the 500 code limit resetting at the end of every quarter. Promo codes will be allowed to have an expiration time lasting up to a year, with the codes be redeemable either via email or from within an app, depending on how the developer chooses to deploy his codes.
Unfortunately, codes will not be available for renewing subscription-based purchases or one-time in-app purchases.