The Cabibbo–Kobayashi–Maskawa (CKM) matrix element $|V_{ub}|$ describes the coupling between $u$ and $b$ quarks in the weak interaction, and is one of the fundamental parameters of the Standard Model. $|V_{ub}|$ is the focus of a longstanding puzzle, as the world-average values derived from inclusive and exclusive $B$-meson decays show a tension of a few standard deviations.

Semileptonic decays can be used to extract CKM elements by combining a lattice QCD calculation of the form factors and experimental branching fractions. In this report we will focus on the recent progress in lattice QCD calculations and the current status of $|V_{ub}|$.