Go to OSX Daily to read How to Prevent Mac from Remembering Wi-Fi Networks Joined
By default the Mac will remember all wi-fi networks that have been joined and accessed from the computer, and will automatically join those wireless networks again when they’re within range. This is a good setting for most users to leave enabled, since it’s convenient to not have to constantly reconnect to familiar wireless networks. But some Mac users may wish to prevent their Mac from remembering joined wi-fi networks, whether for personal, privacy, security, or other reasons.
This article will walk through how to prevent a Mac from remembering wi-fi…
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