The Mosaic project identifies, gathers, harmonizes, and distributes surviving historical census microdata for Europe and beyond. It aims at building a comprehensive and detailed resource for the historic study of populations by historians, demographers, economists, and other researchers. The goal of the Mosaic project is to collect and distribute historical census microdata from regions of Continental Europe where complete centralized records are not available. In gathering censuses of regions, kingdoms, or places where census records were decentrally located and partially surviving, the Mosaic project seeks to put the pieces back together again. 

The Mosaic project was founded by a consortium of historical social scientists in Europe. Data for the project is provided by its partners, which include an international set of institutions in Europe and beyond. Mosaic utilizes data integration and variable harmonization standards of historical integrated census microdata projects such as the Integrated Public Use Microdata Series (IPUMS) and the North Atlantic Population Project (NAPP). Records are distributed in the same integrated format, so that historical comparisons can be made across time and space.