They write: "You can pass the participant ID at the end of the URL as "?PROLIFIC_PID={{%PROLIFIC_PID%}}&SESSION_ID={{%SESSION_ID%}}". We'll replace the {{%PROLIFIC_PID%}} and {{%SESSION_ID%}} with the values of the participants taking part."
I read
this
and
this
but couldn't figure it out on my own.
So how can I fill a hidden question at the start of my survey with information from the referrer url? Any tipps?