First, we have investigated the strain energy response of each monolayer as a function of uniaxial and biaxial strain (Fig. ). The response follows the parabolic path within the elastic range. The narrower and wider strain energy profiles are identified for CrS 2 and CrSe 2 , respectively. Meanwhile, the Janus CrSSe is in between these two monolayers for both modes of strain. This analysis suggests that CrS 2 is the structurally most stable compound under the influence of strain as compared to other monolayers. The figure also proves that the minimum energy state of each monolayer is the strain-free equilibrium state. Additionally, the narrow strain energy curve in the biaxial strain as compared to the uniaxial strain indicates that the biaxial strain has a greater influence on the geometrical configuration. Furthermore, the variation of the bond length and thickness of the MLs are studied under the external strain is shown in Fig. ). It is found that the bond length between the Cr and X (S or Se) atoms monotonically (small fluctuation in CrSe 2 at 2%) with an increase in tensile strain. Conversely, the bond length decreases with the increase of the compressive strain. Similarly, in the strain energy versus strain, the rate of variation of bond length is higher for biaxial strain. The bond length is found to be slightly sensitive towards the uniaxial strain for Janus CrSSe monolayer. This can be ascribed due to the difference in the S and Se atoms on the top and bottom layers. Plus, the difference in bond length and electronegativity may also play a role. The rate of variation of bond length is important to predict the structural strength of a system in external strain. To determine the rate of variation, we test the change of bond length at 12 %, which is within the elastic range. It is found that the rate of variation of Cr-X bond length is in the order of CrSe 2 >CrSSe > CrS 2 . The smaller change in the bond length in CrS 2 indicates that it can withstand the larger tensile strain. On the other hand, the thickness of each monolayer decreases linearly with an increase in strain (small fluctuation in CrSe 2 at 2%).