Background <p>the application of elastic strains is known to change the electrocatalytic activity of materials.</p> Objective <p>this investigation is aimed at developing a experimental strategy to determine how elastic strain affects the hydrogen evolution reaction (HER) in Au and Ag₃In thin films when used as electrocatalysts.</p> Methods <p>A custom-built electrochemical cell was designed and coupled to a uniaxial testing machine so that tensile strains can be applied to the flexible working electrode, enabling us to investigate in situ the effect of elastic strains on the HER activity of Au and Ag₃In thin films when used as electrocatalysts. The actual surface strains were determined by means of the shifts in the main (222) X-ray diffraction peak indicated that the externally applied strains were successfully transferred to both Au and Ag₃In thin films.</p> Results <p>The experimental results show that the in-plane lattice strains reached maximum values of 0.25% in Au and 1.10% in Ag₃In for a maximum applied strain of 1.70%. When the electrodes were subjected to elastic tensile strains, the HER electrocatalytic activity increased.</p> <p>Conculsions: This study showcases how elastic strains can be used to modulate the HER activity of Au and Ag₃In thin films.</p>