Using hyperlink to declare a variable

Online experiments
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I am looking to counterbalance my study, and was wonder if I can modify a variable within the study by utilizing the hyperlink.

For example if my hyperlink is https://run.pavlovia.org/test/study/html

then I could issue different conditions by doing this: https://run.pavlovia.org/test/study/html/?var=1

I can’t seem to get that to work as of yet. Any ideas so far?

Thank you!

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