FAIRsFAIR is supporting 10 European repositories on their journey towards becoming more FAIR-enabling and trustworthy. This includes helping them make and keep their data FAIR and preparing them for the CoreTrustSeal certification as trustworthy repositories. In return, the repositories share their invaluable knowledge on how trustworthy repository practices best enable FAIR data. Their observations and common issues in the certification process help create better guidance and support material for the wider repository community, developing recommendations for integrating FAIR into the CoreTrustSeal requirements.