MOTUS stands for Modular Online Time-Use Survey: a research device for online time-use diary registration combined with on-demand research modules created within a HERCULES-funded infrastructure. High costs of paper-and-pencil diary research prevented to continue the Flemish 1999 and 2004 time-use surveys suitable to scientific needs. The aim of MOTUS is to develop a low cost solution to continue collecting time use data and to design a modular tool that serves different needs in fundamental and applied research. MOTUS generates time use data that can be analysed in various ways, as done with the ‘99 and ‘04 data. The modules’ adaptability allows for any research discipline, governmental body or organisation to link their specific research questions to time-use data.