ClashControl is a free, open-source BIM clash detection web app. Load IFC building models, detect hard and soft (clearance) clashes between disciplines, review every collision in 3D with section planes, and export issues as BCF 2.1 — no install, no license, no subscription. Supports IFC 2x3 and IFC4. Includes IDS validation, data quality checks (BIM basics, ILS, NL-SfB), shared projects without login, and a live link to Revit. Runs fully in the browser and offline as a Progressive Web App.