A screener is a structured qualification instrument placed at the entry point of a research study, designed to verify that each participant matches the audience profile defined during study design. In qualitative research operations, screener quality directly determines sample quality: a poorly written screener admits the wrong participants, and no amount of skilled moderation recovers from that. Effective screeners balance specificity with completion rate, asking enough to confirm fit without signalling the desired answers or creating dropout. They typically cover category usage, purchase behaviour, demographics, and any study-specific criteria such as brand familiarity or product ownership. In enterprise research, screeners also carry a fraud-prevention function, filtering out panel participants who game qualification questions to access incentives.