Background <p>Soft elastomers are widely used in emerging applications such as stretchable electronics and soft robotics, where cracks and flaws can strongly influence mechanical reliability.</p> Methods <p>Here we investigate the fracture mechanics of polydimethylsiloxane (PDMS) by systematically examining the effects of crack depth and crack length on the elastic fields ahead of the crack tip. A combination of theoretical analysis, finite element simulations, and experiments using digital image correlation (DIC) was employed to characterize crack-tip deformation, opening, and evolution.</p> Results <p>The results show that crack geometry plays a critical role in governing crack-tip strain behavior. Shorter or shallower cracks restrict crack opening and blunting, resulting in nearly linear strain fields ahead of the crack tip. In contrast, longer or deeper cracks promote pronounced crack opening and blunting, leading to higher strain magnitudes and asymptotic strain behavior. Three distinct stages during fracture – crack opening, blunting, and propagation – were identified. DIC measurements further revealed that, once propagation begins, the crack advances in a self-similar manner with nearly constant strain and curvature.</p> Conclusions <p>These findings provide new insights into the interplay between crack geometry, nonlinear elastic fields, and fracture evolution in soft elastomers.</p>