Precise measurements of the properties of the top quark test the Standard Model (SM) and can be used to constrain new physics models. The top quark is predicted in the SM to decay almost exclusively into a $W$ boson and a $b$-quark. We present a wide range of searches for non-SM top quark decays using the 13 TeV ATLAS and CMS datasets, including $t\to qH$ and $t\to qZ$. In addition, measurements of the spin correlations, charge asymmetries, top Yukawa coupling and colour flow in $t\bar{t}$ production are also discussed. The latest measurements of the top quark mass using the ATLAS and CMS experiments at the Large Hadron Collider (LHC) are surveyed. A measurement based on a multi-dimensional template fit that can constrain the uncertainties on the energy measurements of jets is presented and combined with measurements using dileptonic and all-hadronic events. In addition, an analysis of the top quark mass using leptonic kinematic variables is reviewed.