Overview of longitudinal studies on Prolific
A longitudinal study is a study that takes place over multiple waves, where the same participants take part in each wave at different points in time.
On Prolific, longitudinal studies are set up as a sequence of waves within a single project. Each wave is a separate study released over time.
Participants must complete Wave 1 and their submission must be approved before they are eligible to take part in Wave 2.
How longitudinal studies work on Prolific
Automatic participant eligibility across waves
Prolific manages which participants can take part in each wave.
Participants with approved submissions for Wave 1 become eligible for Wave 2, and so on.
This removes the need for you to manually manage allowlists between waves.
Upfront setup of all waves
Before launching your longitudinal study, you'll need to create Wave 1 and any additional waves you want participants to progress through.
Important: You cannot add new waves after Wave 1 is published.
You only need Wave 1 to be fully ready before publishing. You can continue drafting and schedule later waves after launch.
Each wave is set up as a separate study, but some settings apply across all waves within the project.
Project-level settings
Some settings are configured once at the project level:
Screeners and participant recruitment
Device requirements
Project details visible to participants
These apply across all waves.
Participant eligibility rules
To access the next wave, participants must:
Complete the previous wave
Have their submission to the previous wave approved
If a submission is rejected or still awaiting approval, the participant will not be eligible for the next wave.
To avoid delays between waves, review and approve submissions before the next wave launches. If you don't, Prolific's 21-day auto-approval window means participants may be approved too late to progress to the next wave on time.
Participant limits across waves
The number of participants you'd like to recruit must stay the same or decrease across waves.
Example:
Wave 1: 100
Wave 2: 80 ✅
Wave 3: 120 ❌
You cannot exceed the number of participants who progressed from the previous wave.
What participants see
Participants can see all waves in your project from the start, including those not yet accepting submissions.
Each wave is displayed with a status:
Completed – Submission completed and approved
In review – Submission awaiting review
Not eligible – Participant cannot access this wave (e.g. screened out earlier or failed to complete previous wave)
Scheduled – Shows when the wave will become available. If the wave is still in draft, participants will only see any entered details (e.g. reward and estimated completion time) or a placeholder message. They can't click into the wave for more details.
Coming soon – Study is not yet published. Participants can see the wave, but details will be limited and will update as you add more information.
This upfront visibility helps participants understand the full commitment, plan ahead, and decide whether to take part. Clear visibility and expectations build participant trust and can improve retention across waves.
How to run a longitudinal study on Prolific
Creating a longitudinal study project
Go to Projects
Select + New project
Enter your project name
Select Longitudinal studies
Click Continue
Adding your recruitment criteria
Select + Add recruitment criteria
Add device or peripheral requirements if relevant
Select + Add screeners
Select the screening criteria participants must meet to take part in your study
Click Save recruitment
Creating Wave 1
Under Wave 1, click Add study
Complete the study setup form:
Study link (URL)
Estimated completion time
Reward
Number of participants
Select Save as draft
Creating Wave 2 and beyond
Click + Add new wave
Click Add study
Complete the setup form
Ensure the number of participants you’d like to recruit is the same or lower than the previous wave
Select Save as draft
Repeat for all waves.
Launching and publishing your study
Before launching:
Ensure all waves are created — you can't create more waves once Wave 1 has been published
Ensure all studies are saved as drafts
To launch your study:
Go to the Project details tab
Click Add project details to add information about your project that will be displayed for participants
Enter the project name
Enter the project overview. This should be a short description about the project which will be displayed to participants.
Enter any additional information participants should know before taking part in your project. This could include anything that may help them decide whether to participate.
Click Publish on Wave 1
Review project details
Check the agreement box
Click Publish
Once published, Wave 1 becomes Active.
Publishing additional waves
You can publish additional waves at any point after Wave 1 is live, as long as they were created before Wave 1 was published.
Important:
Participants must complete waves in order
Each wave unlocks only after the previous is completed and approved
Completing your project
Once you have reviewed all submissions for your final wave, you can mark the project as complete from the Settings tab. This removes the project from participants’ view so they can no longer see or access it, but you can still access and download your data.
Planning your study: Retention Calculator
Set your targets
Final wave goal: Number of participants in your last wave
Target retention rate: % of participants continuing between waves
The default retention rate is set at 80%, but you should calculate a realistic target for your own study. It will vary depending on study length, participant experience, and time between waves.
View projections
The tool shows:
Required recruitment for Wave 1
Expected drop-off between waves
This helps estimate how your sample size decreases over time.
Review costs
The tool provides:
Estimated total project cost
Cost per wave
Cumulative cost across waves
Costs are estimates and may vary depending on actual retention.
Wave breakdown table
Includes:
Each wave in sequence
Expected participants per wave
Estimated drop-off
Cost per wave
Cumulative cost
Best practice guidance
Shorter gaps between waves improve retention
Clear expectations increase completion rates
100% retention is unlikely
Use conservative estimates when planning
Monitoring retention across waves
What is retention tracking?
Retention tracking helps you understand how participants are progressing through each wave of your longitudinal study. It shows whether your study is on track to meet your final completion target, highlights potential retention issues early, and helps you decide whether you need to take action to improve participant return rates.
Understanding retention metrics
Actual retention shows how many participants continued from one wave to the next, compared to your forecasted retention rate. For example, if you expected 68% of participants to return but 90% did, your study is retaining participants better than expected.
Projected completions estimates how many participants are likely to complete the final wave based on your current retention rate. This projection updates as participants progress through each wave.
Shortfall shows how many participants you're projected to be below your final target. A shortfall of 0 means you're currently on track to meet or exceed your target number of completions.
Retention tracking table
Each row in the table represents a wave (study) within your longitudinal project and shows how participant retention is tracking at that stage.
Forecasted participants shows how many participants you expected to reach that wave based on your retention forecast.
Actual participants shows how many participants have actually reached or completed that wave so far.
Variance from target compares the actual participant count against the forecast for that wave. Negative values indicate fewer participants than expected.
Retention rate shows the percentage of participants retained from the previous completed wave.
Health indicates whether retention for that wave is tracking as expected, below forecast, or is still pending because the wave has not yet completed.
Waves marked as Pending do not yet have enough participant data to calculate retention metrics.
What to do if retention is lower than expected
If there's a projected shortfall, you can take steps to improve retention and help more participants reach later waves. For example, you can:
Increase places in earlier waves to increase the pool of eligible participants
Review and approve submissions promptly, so participants can access the next wave without delay
Message eligible participants to remind or encourage them to take part in upcoming waves
Consider offering a completion bonus to encourage retention, but don't rely on compensation alone. Be clear about any bonus requirements from the outset, and remember that if waves are less than 21 days apart, you'll need to manually approve submissions before participants can progress to the next wave.
Alternatively, you can choose not to take further action and continue with fewer final wave submissions than your original goal.