Using Critical Path in Gantt

When you click Critical Path button , the latest task that ends on or after the project end date is highlighted in the Gantt chart. Other tasks that are dependent on this task are also highlighted. Changing the end date or duration of any task in the critical path could affect the end date of the project.

We recommend that you:

Select the preference Adjust this project's end date automatically. Open the Preferences dialog to do this. If you change tasks dates or durations, the project end date is adjusted to the end date of the last task and the project's critical path is always highlighted.
Turn off the critical path when you are making changes to your project.
Add dependencies between tasks.

Note: If you change the work calendar of a task to be different from the other tasks in the critical path, the critical path might not display correctly.