A measurement of the forward–backward asymmetry ${A}{\mathrm{FB}}$ of oppositely charged lepton pairs ( $\mu \mu $ and $\mathrm{e}\mathrm{e}$ ) produced via $\mathrm{Z}/\gamma ^*$ boson exchange in pp collisions at $\sqrt{s} = 8$ $,\mathrm{TeV}$ is presented. The data sample corresponds to an integrated luminosity of 19.7 $,\mathrm{fb}^{-1}$ collected with the CMS detector at the LHC. The measurement of ${A}{\mathrm{FB}}$ is performed for dilepton masses between 40 $,\text {GeV}$ and 2 $,\mathrm{TeV}$ and for dilepton rapidity up to 5. The ${A}_{\mathrm{FB}}$ measurements as a function of dilepton mass and rapidity are compared with the standard model predictions.