We introduce a quantum loop group associated to a general symmetric Cartan matrix, by imposing just enough relations between the usual generators {e_{i,k},f_{i,k}}_{i\in I,,k\in\mathbb{Z}} in order for the natural Hopf pairing between the positive and negative halves of the quantum loop group to be perfect. As an application, we describe the localized 𝐾-theoretic Hall algebra of any quiver without loops, endowed with a particularly important \mathbb{C}^{*} action.