Ensure that the tailscale app is logged out before proceeding.
Go to iOS settings, scroll down past game center and tv provider to the tailscale app and select it. The headscale URL can be entered into the _"ALTERNATE COORDINATION SERVER URL"_ box.
> **Note**
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> If the app was previously logged into tailscale, toggle on the _Reset Keychain_ switch.
Restart the app by closing it from the iOS app switcher, open the app and select the regular _Sign in_ option (non-SSO), and it should open up to the headscale authentication page.
Enter your credentials and log in. Headscale should now be working on your iOS device.