I have a widget that people will install on their websites and I want to implement a tracking method to see the domains where the widget is installed. I know I could just include a tracking pixel and track the hits on my server, but since I anticipate 50k+ installs of the widget, this would cause a lot of stress on my server.
Is there a tracking service that can be used for this situation?
If you can place small javascript to run inside your widget you may try this tool--check out the referral segmentation example. Note that it does not provide any UI with graphs like Google Analytics or similar services. It's just an API and small language to query collected events.