A measurement of the W boson pair production cross section in proton-proton collisions at $$\sqrt{s} = 8$$ TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 19.4 $$\,\text {fb}^\text {-1}$$ . The $${{\mathrm{W} }^{+} }\mathrm{W}^{-} $$ candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured $${{\mathrm{W} }^{+} }\mathrm{W}^{-} $$ cross section is $$60.1\pm 0.9\,\text {(stat)} \pm 3.2\,\text {(exp)} \pm 3.1\,\text {(theo)} \pm 1.6\,\text {(lumi)} \text {\,pb} = 60.1\pm 4.8\text {\,pb} $$ , consistent with the standard model prediction. The $${{\mathrm{W} }^{+} }\mathrm{W}^{-} $$ cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are $$-5.7< c_{\mathrm {WWW}}/\Lambda ^2 < 5.9\,\mathrm{TeV}^{-2}$$ , $$-11.4< c_{\mathrm {W}}/\Lambda ^2 < 5.4\,\mathrm{TeV}^{-2}$$ , $$-29.2< c_{\mathrm {B}}/\Lambda ^2 < 23.9\,\mathrm{TeV}^{-2}$$ , in the HISZ basis.