Precision QCD at HERA

HERA was a high-energy electron/positron proton collider with a centre of mass energy of up to 320 GeV operated until summer 2007. The hadronic final state in the regime of deep-inelastic scattering as well as of photoproduction has been thoroughly investigated over a wide range of phase space with the two multi-purpose detectors H1 and ZEUS. The large available HERA data samples of about 0.5 fb−1 per experiment allowed stringent tests of quantum chromodynamics using a variety of different observables connected to the production of jets and heavy quarks. From the jet production measurements the strong coupling constant αs has been extracted with high precision. Some of the most recent results of the H1 and ZEUS collaborations are presented in this contribution.