session cookie problem?

[JensBoelte]

Hello

I currently conduct four online experiments for my research class. I run the experiments via Pavlovia. I direct students to https://studien.uni-muenster.de/ for credits, as Pavlovia surveys lack the feature to send emails.

The problem is that some participants who run more than one experiment do not receive credits for their second or third participation. It seems that the students are entering the end of the experiment instead of the start.

I have already set the cookie lifespan to three minutes, but this did not solve the problem.

I created my own random session code and passed it as a URL parameter (e.g. https://studien.uni-muenster.de/VPStunde/?exp=VpKodeFormR&VPn=001&VPCode=21PINEDA&code=J~c1rp4XaPu20~Rmmb0grDhOjV+~kdKC2sF5KZ8RVnwD6frnVjlYBlPe2EdpBLq1). This did not help either, as form-r complains that the user code is invalid and that the session needs to match.

Do you have any ideas on how I could solve this problem?

Best wishes Jens

[cyriltata]

Dear Jens, I think they will need to delete the formr cookies on their browsers to use the same device to participate in the same study, Or you could add a link at the end of the run (in a Stop Unit) maybe <study-url>/logout. Where this can delete the cookie. best Cyril

…

On Tue, Nov 11, 2025 at 4:54 PM Jens Bölte ***@***.***> wrote: Hello I currently conduct four online experiments for my research class. I run the experiments via Pavlovia. I direct students to https://studien.uni-muenster.de/ for credits, as Pavlovia surveys lack the feature to send emails. The problem is that some participants who run more than one experiment do not receive credits for their second or third participation. It seems that the students are entering the end of the experiment instead of the start. I have already set the cookie lifespan to three minutes, but this did not solve the problem. I created my own random session code and passed it as a URL parameter (e.g. https://studien.uni-muenster.de/VPStunde/?exp=VpKodeFormR&VPn=001&VPCode=21PINEDA&code=J~c1rp4XaPu20~Rmmb0grDhOjV+~kdKC2sF5KZ8RVnwD6frnVjlYBlPe2EdpBLq1). This did not help either, as form-r complains that the user code is invalid and that the session needs to match. Do you have any ideas on how I could solve this problem? Best wishes Jens — Reply to this email directly, view it on GitHub <#633>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AARL5Z72NJ4WTSTWSYHSTJL34IBEVAVCNFSM6AAAAACLZGJI4CVHI2DSMVQWIX3LMV43ERDJONRXK43TNFXW4OZZGEZDSOBXGA> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[JensBoelte]

Hello

I think they will need to delete the formr cookies on their browsers to use the same device to participate in the same study,

There is no way that I can get participants to delete cookies on their browsers.

Is there any way to influence the lifetime of this cookie?

Best wishes Jens

[JensBoelte]

Hi

thanks a lot for this tip about a link in as Stop unit. I realised it but I am still running in the same problem. I assume that participants do not use this to "log out".

I wonder if there is a way to delete the session cookies regardless of whether the participant looks out or not. I have some JavaScript code which should delete the cookies. But I am unsure were to insert it in the run?

In a Stop-Unit, before the Stop-Unit or via Settings - JS?

Best wishes Jens
In

[cyriltata]

the cookie in question is not accessible by Javascript

…

On Sun, Nov 16, 2025, 17:58 Jens Bölte ***@***.***> wrote: Hi thanks a lot for this tip about a link in as Stop unit. I realised it but I am still running in the same problem. I assume that participant do not use this to "lock" out. I wonder if there is a way to delete the session cookies regardless of whether the participant looks out or not. I have some JavaScript code which should delete the cookies. But I am unsure were to insert it in the run? In a Stop-Unit, before the Stop-Unit or via Settings - JS? Best wishes Jens In — Reply to this email directly, view it on GitHub <#633 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AARL5Z4WQOCIQ62STFWVFZT35CULVAVCNFSM6AAAAACLZGJI4CVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIOJYGI2DCOI> . You are receiving this because you commented.Message ID: ***@***.***>

[rubenarslan]

HI Jens,

you have the following options:

1. Use an External module at the end of the procedure to send them to the YOURSTUDY/logout link. That will destroy the session cookie and send them to a page saying the session has ended.
2. Generate your own valid codes, matching the RegEx: ^[A-Za-z0-9+-_~]{64}$. You did this, but you did URLEncode it (in your case, the code contains a plus sign which would need to be changed to %2b. It's probably easier to just generate alphanumeric codes without special characters, they are optional.
3. Alternatively to the redirect, if you want more control over the last run page, you can do <iframe src="https://studien.uni-muenster.de/VPStunde/logout" style="display:none"></iframe> in a Stop button on the last page. I haven't tested this cross-browser.
   Best wishes,

Ruben Arslan

[JensBoelte]

Hello Ruben

Thanks a lot for your suggestion.

Suggestion 1 could probably work. However, there is a backlink on this page that takes you back to the study. Therefore, participants could potentially return to where they came from.

I tried to implement suggestion 3 with Daniela Feistauer's help here in Münster, but the result was not the desired layout or appearance.

Let's see if suggestion 2 solves the problem. I'm not very familiar with formr. So it's quite possible that I won't be able to implement the suggestions very well.

Best wishes Jens