It is possible to recover the password of a WiFi network on which you have already connected in the past. Here is how to proceed according to your operating system.
You go to a café or a friend’s house, you connect to the WiFi network and one day you come back with another device and you are either too lazy or too shy to ask for the password again. If you still have the first device in your possession, whether it’s a smartphone or a computer, you can find the password you looking for and use it on your new device.

How to find wifi passeword on windows
Active connection
Go to Control Panel > Network and Internet > Network and Sharing.
Click on the active WiFi connection and then on Wireless Properties.
Click on the Security tab and on “Show characters”, the password of the WiFi network you are connected to will be revealed.
Note that this method only works on the networks you are currently connected to. If you are looking for the password of a network you connected to some time ago, follow the steps below.
View passwords in command lines
Start the command prompt.
Enter “netsh wlan show profiles” to view the WiFi networks you have already connected to.
Enter “netsh wlan show profile name=<<WiFi network name>> key=clear” replacing <<WiFi network name>> with the name of the network you discovered with the previous command.
In the Security parameter, search for “Key content”, you will get the desired password.

how to see wifi passeword on macOs
Press Command + Space to open Spotlight, search for “keychain access,” and open the app. Then, use the search bar in the Keychain Access app to search for the name of any Wi-Fi network you’ve connected to in the past. When you see the network in the list, double-click on it to see its password entry. You’ll need to check the Show Password box along the bottom to see the password in plain text.

How to find Wi-Fi Passeword on Android
Launch the Settings application and go to Network & Internet > WiFi. Select the network in question or tap on “Saved Networks” to see the password of an old network. Tap on the Share button and under the QR Code you will see the password. If there is no password under the QR Code, display the QR Code, download and install (if needed) a QR Code scanner, and the password should be visible once the QR Code is scanned. That said, this method only works on devices running Android 10 or later. If you have a smartphone running an older version, you’ll have to do things differently (including getting root access).
How to see Wi-Fi passeword on Iphone

Then you have to start a scan, and after a few minutes you will see the passwords directly on your computer screen.
The software can also export the icloud keychain in csv format.