•Chemically reactive flow of Williamson nanofluid by a nonlinear stretched surface.•Nanomaterial model comprises thermophoresis parameter and Brownian motion.•Bidirectional nonlinear stretching sheet of constant thickness is considered.•Non-uniform applied magnetic field is in z-direction. Main theme of this article is to model and analyze the outcome of chemically reactive flow of nanomaterial. Nanomaterial comprises thermophoresis and Brownian motion. Bidirectional nonlinear stretching sheet of constant thickness is considered. Rheological expressions of Williamson fluid is used to develop formulation. Boundary layer approach and suitable transformations are utilized to simplify the governing equations. Optimal homotopy analysis method OHAM is utilized for values of convergence control parameters. Tabulated values of skin friction coefficients and Nusselt and Sherwood numbers via different parameters are calculated and examined. Physical features of various pertinent parameters are argued through graphs. It is observed that velocity decays in x-direction for higher values of magnetic parameter. Temperature and concentration have contrast behavior for larger Brownian motion.