As you surely know, Microsoft released at Microsoft Ignite the SharePoint Migration Assessment Tool (SMAT). SMAT is a tool that allows to do a deeply scanning of your SharePoint 2013 farm and find potential issues and problems when migrating to SharePoint Online in Office 365. You can download SMAT from the following URL:
https://www.microsoft.com/en-us/download/details.aspx?id=53598
You will also find additional details about SMAT in the download page: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 with out 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 process in the console window. After the scan is complete, you can find output files in the tools directory that will give you summary and more detailed insights into the scenarios that could be impacted by migration