Keychains is the utility that macOS has to store all passwords that you use on your computer and to be able to access websites, emails, etc. that they ask you for validation to enter; that is: a username and password.
Surely, on more than one occasion, at the end of your authentication in a service, a window has assaulted you asking if you want to save this password. If you accept, it will be "Keychain Access" who stores it and offers it to you every time you need it. However, it is quite possible that on some occasion, for whatever reason, you need to see what password did you choose for that service. Here we show you how to see each of them using the macOS application.
First of all, let you know that In order to see each password, the system will ask you for the same one that you use to open the system after a rest or a new login. Without this password it will be impossible for you to access the information you request. It is one more step, yes, but it is also one more security method for those outside eyes or those who want to access your computer. But let's go on to detail what you should do in this regard:
First thing: go to Keychain Access. You can access this application in different ways: using Spotlight; the Launchpad on the Dock or via Finder> Applications> Utilities. Once you find it, access it. Once inside, a new window will appear with the entire list of passwords, certificates, keys, notes —the ones you use encrypted by means of a password—, etc.
Well, in order to see any of the passwords you want, choose the service you need to consult from the right list. Access with a double click and in the new window that appears, in the lower left corner you will have a box that you must check that indicates: "Show password". When you press it, the system will ask you to enter your login password and when you accept the password for that service will appear in that same box.