Madaster, a circular construction organisation that aims to ‘make materials available forever by giving them an identity’, has partnered with the Amsterdam Metropolitan Area to initiate a materials passports pilot project. The enterprise strives to create value in materials used for construction—an industry characterised by excessive waste generation—and ultimately stimulate circular construction in the region. Madaster serves as a public, digital platform that catalogues the products and materials used in a building, thus creating documented ‘storage units’ of materials that are easy to recover and reuse. Circular and financial information flows are also linked, which records past, present and future values of such materials. So far under the project, eight Amsterdam municipalities have been awarded certificates for their implementation of materials passports.