Harmonising variables is an important part of social science research. It adds value to existing dataset through its reuse and extends compatibility to other datasets. However, these intellectual contributions are often lost because researchers can’t publish their work. For variable harmonisation work to be of scientific value the harmonisation process must be documented and published in a precise and transparent ways, and different types of harmonisations must be comparable (e.g. SPSS, CharmStats or DDI). The simplification and routinisation of data harmonisation workflows will create better data synergies. Winters and Netscher published standards for documenting variable harmonisation work but a digital location for harmonisation work is needed. Our solution is an online library where digitally documented harmonisation routines will be archived and accessed. The Library of Online Harmonizations will advance data harmonisation by transforming it into a digital documentation process of outputs that are publishable, findable, citable and replicable using only online resources. Such a platform requires metadata and data harmonisation workflow to be represented in a standardised and machine actionable way. We will present how DDI can be utilized in in the creation of the Library of Online Harmonisations.