Your Mac automatically remembers W-Fi networks that are connected to the past. However, automatically connected networks may not be the best choice. Here’s what to do if you want your Mac to forget the Wi-Fi network.
Besides erasing old connections, forgetting Wi-Fi networks can help you solve connection problems. If a network has changed its password and your Mac doesn’t give you a password prompt (or if it’s just a splinter), you can try to forget and rejoin the network.
To do this, click the Wi-Fi icon in your Mac’s menu bar, then select “Open Network Preferences.”
Here, click “Advanced.”
Under the “Wi-Fi” tab, scroll and select the network that you want your Mac to forget, then click the minus sign (-).
At the prompt, click “Delete” to forget the network. This will remove network login credentials from your iCloud Keychain, too, making it accessible to all of your other Apple devices.
Click “OK” on the Wi-Fi screen.
Click “Apply” in the Network window to save your changes.
Your Mac has now forgotten the Wi-Fi network. If you want, you can click the Wi-Fi icon in the menu bar to log in to the network again.
If you use multiple Wi-Fi networks in the same location (like your home or office), you might not want your Mac to forget it. In this case, you can prioritize the ones you use the most.