It is possible to run a study on Prolific without a completion URL. In this case, please include the following instruction in your study description:

"Dear participant,
There will not be a completion URL at the end of this study. Please make sure to click on the green "I've finished"-button when you have completed the study. If you fail to click on this button upon finishing this study, then we may not be able to compensate you for your time. Thanks!"

The reason why it's important to click on this button or on the completion URL is that it signals to the system how many people take part, so we can fill your quota. Without this mechanism, the system wouldn't know when to stop allowing new participants.

Did this answer your question?