Gantt Scheduler is project management software that addresses resource-constrained scheduling through optimization algorithms. The software considers real-world constraints like team size to create realistic timelines. Powered by Google OR-Tools CP-SAT solver, it finds optimal schedules or best-effort approximations within time limits. The software starts with an Excel template where tasks, durations, dependencies, and resource needs are inputted. Supporting Excel, LibreOffice, and Microsoft Project XML files, it handles all predecessor types with optional lag or lead values. Gantt Scheduler offers modes to find the earliest finish date, calculate required headcount for deadlines, or explore schedule compression. An interactive Gantt chart enables task pinning and re-optimization, with color-coded visuals showing conflicts. The software preserves Microsoft Project structures and requires no account or file storage.