BLOCKS: An adaptable application for administering blocked, text-based vignette experiments

BLOCKS is an open-source, web-based application for administering blocked, text-based vignette experiments. Researchers prepare the blocked vignette design using their preferred statistical or programming software. The selected block structure and outcome measures are then implemented in BLOCKS through plain-text vignette files organised into vignette set-specific folders and structured Excel workbooks. At runtime, BLOCKS configures the online experiment from these file-based inputs, uses adaptive assignment to the least-occupied vignette set, with random tie-breaking, randomises vignette order within sets, validates responses, records attention-check results, stores data in a relational database, captures process-generated data such as response latency, click counts, answer changes, and timestamps, and provides protected CSV export. By separating researcher-defined study configuration from the web-application logic that administers the study, BLOCKS lowers implementation barriers so researchers can focus on substantive expertise. The software supports transparent and reproducible implementation through inspectable file-based inputs, version-controlled workflows, and structured data export, with open access and archival provided through GitHub and Zenodo.