  This document aims to provide an assessment of the potential of future
colliding beam facilities to perform Higgs boson studies. The analysis builds
on the submissions made by the proponents of future colliders to the European
Strategy Update process, and takes as its point of departure the results
expected at the completion of the HL-LHC program. This report presents
quantitative results on many aspects of Higgs physics for future collider
projects of sufficient maturity using uniform methodologies. A first version of
this report was prepared for the purposes of discussion at the Open Symposium
in Granada (13-16/05/2019). Comments and feedback received led to the
consideration of additional run scenarios as well as a refined analysis of the
impact of electroweak measurements on the Higgs coupling extraction.
