If you’re browsing the Web and need to either create a new account or log into an existing one, then you will likely need to enter your password. To help with this, OS X will prompt you to store your password in the OS X keychain, which will encrypt and assign the password to the site you have just accessed. This is similarly applied to programs you may use, such as e-mail clients, which will attempt to access secured resources like your e-mail accounts or social media pages. However, the convenience this provides may result in your inability to remember your passwords, even for sites you regularly frequent.
An additional step of removal from keeping track of your passwords is that the keychain will automatically generate high-quality passwords, that are essentially random strings of characters that are exceptionally difficult to memorize. With this and the keychain’s auto-entry of passwords, if you access your account from a new computer or a program that does not support the keychain, then you may not know where to start. Granted you can use your account’s password reset options on the new system, which sometimes may be the only option, but this will prevent your Mac from accessing the account.
Open Safari and press Command-, to go to its preferences. In here, select the Passwords tab, and then search for the Web site you are interested in. Select the site, and then click the checkbox to show the password for selected sites. Authenticate when prompted, and your password will be revealed, which you can then write down for use on your second computer.
You can also right-click the password entry and choose the option to copy your password to the clipboard, which will require you authenticate, but then be able to paste your password in a password entry field.
If you do not use Safari, then you can access this same information using your Mac’s keychain. Open the Keychain Access utility and then select “Passwords” in the left-hand column. Then perform a search for the Web URL you are interested in, and select the appropriate password entry for it. You may have this site configured with applications other than your Web browser, so you may see application password entries along with Web form password entries listed. It does not matter which entries you choose, provided it holds the account information you want.
To reveal the password, double-click the entry to open it, and then click the “Show password” checkbox, followed by supplying your Mac’s account password when prompted. Alternatively, as with the Safari password list, you can right-click the entry and choose the option to copy the password to the clipboard (or press Shift-Command-C), and then you can paste the password into another program.