Pra-populate registration field by URL

Anyone knows how to

1) pre-populate a field on the registration form by adding a tag to the URL?

2) Can this field even be hidden?

Usecase is to distribute these URLs to recruiters who want to share this link directly to make sure people who subscribed via them can be tracked correctly.

1) pre-populate a field on the registration form by adding a tag to the URL?

You'd need to use CB Auto Actions to do this. You'll need to use a Code action with Method set to jQuery on the before registration display trigger. You'd then use jQuery to set a fields value. To condition based off a URL variable you can check against GET values in your actions conditional with "[get_VARIABLE] Equal to VALUE". This usage is somewhere on the forums as another user wanted it too.

2) Can this field even be hidden?

You can hide it with CSS or hide it with jQuery after setting its value.

Usecase is to distribute these URLs to recruiters who want to share this link directly to make sure people who subscribed via them can be tracked correctly.

Probably better to just use an affiliate extension and have the extension redirect to CB registration after using the link.