It is possible to see the passwords that you have saved for WiFi networks you have previously connected to. Here, you will find out how to see them. Keep in mind that it in order to get direct access to the WiFi passwords saved on iPhone or any iOS device, jailbreaking may be required. This is a process that should be followed carefully and under your own risk as it could void your device’s warranty.
You can use iPhone apps such as 1Password to save your WiFi network password.
If your Mac is connected to the same WiFi network you will be able to find the stored passwords in Keychain access app.
If you are using an Apple Airport based device, you can log directly into it using AirPort utility to see the password at source.
You can also use iCloud keychain syncing to sync your iPhone or iPad saved WiFi password to another device such as Mac and you can read the password in Mac keychain as in option 1.
After that on Mac, enable keychain syncing via System Preferences. Then iCloud preferences and use keychain utility to check the iCloud keychain.
You can see the saved WiFi password on jailbreak iPhone. If your iPhone is jailbroken, check the WiFi Passwords on Cydia. This lets you see the username and password for WiFi network.
You can also try to install NetworkList from Cydia, this is a practical tweak that allows you to find stored passwords on iOS 8 go to Settings, then WiFi, folowed by Network passwords) or Settings, then WiFi, Known Networks, depending on the iOS version that is running on your device.