Someone keeps sending me a link via bluetooth - how to stop them without disabling bluetooth?
This is Handoff, part of Continuity, where devices signed into the same primary iCloud account can ‘hand off’ currently viewed content between each other.

Handoff isn't available for anyone to share content with you — this is only for you to share content between your own devices. I would be very concerned that someone has access to my iCloud account on a supposedly unknown device. I recommend investigating this further if you are unaware of the Continuity source.

You can disable all Continuity features including Handoff in System Preferences → General → Allow Handoff between this Mac and your iCloud devices.