Wifi Password Recovery is a free app that can help you find and retrieve the passwords of all the Wi-Fi networks you have ever connected to. It's one of the best Wi-Fi password retrieving apps that are currently available in the Google Play Store. 

How to use it:

• Open the Wifi Password Recovery app on your phone
• The app will provide you with a list of all the networks you connected before.
• Choose the Wi-fi ID, and the password dialog will appear.
• Tap the copy button to copy the password to be able to connect to the network.

The app can be downloaded for free on Android devices.