Prolific does not include built-in tools for random assignment of participants to different study conditions.
If your study has multiple conditions (for example, control and experimental groups), you must handle random assignment within your study software or another external tool.
What Prolific supports
Prolific sends participants to your external study link
Randomization and condition assignment must happen within your study platform
Prolific does not manage condition quotas across multiple study links
If you run separate Prolific studies or use different study URLs for each condition, participants may start at similar times. This can lead to uneven group sizes.
Recommended approach
Use the randomization tools in your study software. Many survey and experiment platforms (such as Qualtrics, and Gorilla) include built-in random assignment features.
These tools allow you to:
Assign participants to conditions
Record condition labels in your dataset
To reduce the risk of uneven condition sizes, researchers typically use a single Prolific study link and randomize participants after they enter the study.
Before launching
Test your randomization setup before collecting data. Running a small pilot can help confirm that participants are assigned to conditions correctly. See: How do I run a pilot study?