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On macOS, find the ZeroTier app in your menu bar. Launch the ZeroTier One app bundle if it's not already running. Click the ⏁ icon on your menu bar and select Join Network.
On Windows, the ZeroTier one UI app lives in the system tray. Right click on the ZeroTier icon and select Join Network.
Additionally, with the macOS and Windows user interfaces, you can easily re-join networks that you've previously left.
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