A "promo code" is a long alphanumeric code that can be redeemed for a FREE copy of a specific app for iOS or Android. Developers are given a limited number of codes for each version of an app they submit to Apple, or each quarter on Google Play. These codes are only valid for 28 days once they are generated by the developer, but once redeemed on your account, the app is yours forever. Apps "purchased" with promo codes are just like regularly purchased apps with one exception: you cannot write a review on the App Store for these apps (but you can on Google Play). You will continue to receive free updates to these apps and they will remain attached to your Apple ID or Google account indefinitely.
How Do I Redeem a Promo Code?
First, make sure you are connected to the Internet via wi-fi or 3G.
On an Apple device running iOS 11 or newer:
On iOS 11 or newer devices, go to the App Store, tap Today at the bottom, look for your Apple ID icon in the top right corner (your picture or a profile icon) - or alternatively, go to the very bottom of the Today tab, tap Redeem, and enter the code. (You actually have to touch the text "You can also enter your code manually" to enter the code manually.)
On an Apple device running older iOS versions:
Go to the App Store, find the (2) Featured tab, and scroll all the way to the bottom. There you will find a button that says (3) "Redeem" - touch it to bring up the window where you'll (4) put your code. You may be prompted to enter your password. Touch the text that says "You can also enter your code manually" to enter the code. If the code is valid, the app will begin downloading to your device.
These instructions are taken from the Apple App Store support article: https://support.apple.com/en-ca/HT201209.
On an Android device:
Open the Google Play Store app, tap the Menu, then Redeem. Enter your code and hit Redeem. The app will download.
These instructions are taken from the Google Play Store support article: https://support.google.com/googleplay/answer/3422659?hl=en
Troubleshooting: If your code does not work or says "invalid code", try closing your App Store. Restart the store app and try again. If it still doesn't work, try restarting the device. If it won't work after that, please contact us for a new code.
If you are a blogger, presenter, researcher, university clinic director, app reviewer, or app review committee member for volume purchases, please contact us about free promo codes for your needs. And please, if you are given a code, do remember to redeem it within 28 days!