On paid offers, by default your city, region/state, country and IP address are shared with the domain owner. 

On your settings page you can opt-out of sharing any information with the domain owner. However, some owners will not negotiate with buyers who do not provide that basic information.

Your name, email address, telephone number, company and postal address are not shared at any point.

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On free offers, your full contact information is shared with the domain owner.