The SharePoint Migration assessment tool (SMAT) is a simple command line executable that will scan the contents of your SharePoint farm to help identify the impact of migrating your server to SharePoint Online with Office 365. Because the tool is designed to run without impacting your environment, you may observe the tool requires one to two days to complete a scan of your environment. During this time, the tool will report progress in the console window.
After the scan is complete, you can find output files in the Logs directory. This is where you will find the summary and more detailed insights into the scenarios that could be impacted by migration.
Learn more and download the SMAT here.