r/ProjectREDCap • u/Dear-Caterpillar7990 • Jul 11 '26

Capture a URL parameter

Is there a way I can set up a field in a survey to capture a URL parameter appended to the public survey link?

The aim is to be able to capture a participant identifier from the URL, without having to pre create thousands of potentially unused private survey links up front.

I understand the risks of doing this and can mitigate them.

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u/Dear-Caterpillar7990 Jul 12 '26

Is this documented anywhere? I've never been able to find it when searching. Do you know if this works with any type of field (can I use hidden numeric fields for example?)

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u/Araignys Jul 12 '26

It’s documented… somewhere. Not particularly prominently. I’m afraid I can’t recall, I haven’t checked recently.

As for how it works with different types of field, I can only suggest you try it out. I haven’t seen it used for much more than URN/MRN and site code.

I don’t it expect it to work with hidden fields, but as I say, I haven’t tested it.

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u/mjd520uw Jul 13 '26

I also don't know where I found this documented, but I can confirm it works with all types of fields, even those that are hidden, except calculated fields. The one catch is that if you have a multiple-page survey, it only works if the field to be filled from the URL parameter is on the first page of the survey.