Background: Flat foot is a dysfunction of the posterior tibial tendon and spring ligament which cause excessive pronation of foot, resulting reduce shock absorption. Objective: This study determines the lower extremity mechanics of normal and flat foot adults by using Gait On software application. Method: A cross-sectional study was conducted involving 32 undergraduate students aged 18–25 from Brainware University. Participants will be screened using the Chippaux- Smirak Index (CSI) to classify foot posture. Gait was analyzed using video capture and software-based analysis. Comparisons were made between flat-footed and normal-footed individuals across gait parameters. Result: ANOVA analysis revealed significant differences (p < 0.05) across all stance phase subphases between flat feet and normal feet groups. Mann-Whitney U test showed significant CSI score differences (p < 0.00001). Flat feet individuals demonstrated strong correlations between CSI scores and terminal swing (r = 0.70) and pre-swing phases (r = 0.60), with negative mid-stance correlations (r = -0.59). Normal feet individuals showed weaker correlations across all phases. Conclusion: Flat feet individuals exhibit significant biomechanical alterations throughout stance phases with severity-dependent gait changes. Structural foot abnormalities create systematic compensatory movement patterns affecting the lower kinetic chain. Results support comprehensive gait assessment needs and early intervention strategies for flat feet populations.