A free app for Android, by Maxisofthub.

Wifi Password Show Master key is an app that lets you view all the saved passwords for the WiFi networks you’ve connected your Android device to. This app is not for hacking WiFi networks or anything like that. It’s simply to see the passwords you’ve already entered for networks you’ve already connected to.

This app requires root privileges to work, and it also needs the permission to access the network and the storage. It doesn’t store any information in its database, and it doesn’t use or share any kind of user personal information with any third party.