# Missing Participant IDs via Prolific

**URL:** <https://discourse.psychopy.org/t/missing-participant-ids-via-prolific/45253>\
**Category:** Online experiments\
**Created:** [July 22, 2025, 3:41pm UTC](https://discourse.psychopy.org/t/missing-participant-ids-via-prolific/45253 "2025-07-22T15:41:20Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![helenr](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/helenr/32/15631_2.png) [@helenr](https://discourse.psychopy.org/u/helenr)\
**Post date:** [July 22, 2025, 3:41pm UTC](https://discourse.psychopy.org/t/missing-participant-ids-via-prolific/45253/1 "2025-07-22T15:41:20Z")

</div>

I’ve encountered an issue while running an experiment on Pavlovia with participants recruited via Prolific. I’ve used this setup successfully many times before, but this is the first time I’ve seen this problem.

The experiment uses URL parameters to record Prolific IDs. Out of 40 participants who completed the study, 19 have missing Prolific IDs in their dataset — although all other data was recorded correctly. The remaining 21 participants have their Prolific IDs recorded as expected.

I can potentially match the missing IDs using timestamps, but I’m concerned this may indicate a broader issue. If the URL parameters weren’t passed correctly, why would they work for some participants and not others?

---

<div class="post-metadata">

**Author:** ![wakecarter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/wakecarter/32/5753_2.png) [@wakecarter](https://discourse.psychopy.org/u/wakecarter)\
**Post date:** [July 22, 2025, 10:15pm UTC](https://discourse.psychopy.org/t/missing-participant-ids-via-prolific/45253/2 "2025-07-22T22:15:17Z")

</div>

Please check these tips.

> [@Wakefield's Daily Tips](https://discourse.psychopy.org/t/wakefields-daily-tips/43371/8):
>
> Exit cleanly Locally you might want your participant to end on a thank you screen rather than being sent back to the PsychoPy Builder. Unfortunately, this desire has encouraged a bad habit of leaving the final message on screen and then pressing the escape button to exit. While data is saved locally after escape has been pressed, until recently microphone recordings were not. My recommendation would be to have the final screen end on a key press that you have not told the participant, e.g. ‘q’. …

> [@Wakefield's Daily Tips](https://discourse.psychopy.org/t/wakefields-daily-tips/43371/35):
>
> Daisy Chaining Daisy chaining means going from one web application to another in a single participant session. It normally requires passing the values of one or more variables from one app. to the next so that the data can be matched. There are two aspects to consider. The first is sending values TO Pavlovia. I highly recommend that you send a value for participant (without changing the spelling or capitalisation) since this value will start the data file and log file names. A column for sessi…