We review the ALPHA collaboration strategy for obtaining the QCD coupling at high scale. In the three-flavor effective theory it avoids the use of perturbation theory at α>0.2 and at the same time has the physical scales small compared to the cutoff 1/a in all stages of the computation. The result \Lambda_\overline{MS}^{(3)}=332(14)~MeV is translated to \alpha_\overline{MS}(m_Z)=0.1179(10)(2) by use of (high order) perturbative relations between the effective theory couplings at the charm and beauty quark "thresholds". The error of this perturbative step is discussed and estimated as 0.0002.
@article{arxiv.1611.05750,
title = {The determination of $\alpha_s$ by the ALPHA collaboration},
author = {Mattia Bruno and Mattia Dalla Brida and Patrick Fritzsch and Tomasz Korzec and Alberto Ramos and Stefan Schaefer and Hubert Simma and Stefan Sint and Rainer Sommer},
journal= {arXiv preprint arXiv:1611.05750},
year = {2016}
}