The Joint Evaluated Fission and Fusion File (JEFF) Nuclear Data Library Project is a collaboration between NEA Data Bank participating countries. The JEFF library combines the efforts of its different working groups to produce a common set of evaluated nuclear data, mainly for fission and fusion applications. The JEFF project meets twice a year, in autumn and spring. The April 2021 Nuclear Data Week will host the JEFF Co-ordination Group meetings and a selection of JEFF technical sessions.