# Participant Groups

Participant groups are saved groups of participant IDs, so you can re-contact the exact same
participants across studies. They are dynamic in nature, so you can add and remove participants from the group on the fly and
any studies published with a participant group allowlist or participant group blocklist filter will be updated automatically.
Participant groups allow you do the following:

* Create a new participant group within the scope of a project.
* Add and remove users manually to / from the participant group.
* Use one or more participant groups as allowlist or blocklist filters for a new study.
* Combined with study completion codes, automatically add or remove participants from a group
  when they submit a response to your study with the correct code.
* Any participants added to or removed from the participant group on the fly will be automatically
  eligible or ineligible for studies that use a participant group allowlist or blocklist filter.