Today I Learned: Microsoft is Increasing Their URL Path Length Restrictions
Microsoft has announced that they are increasing the URL path length restriction from 256 units to 400. The new limit section will apply to the total length of the URL path. This includes all SharePoint Online and OneDrive for Business URLS. In addition, Microsoft is now supporting # and % characters in the file and folder names. This will allow you to more effectively organize your files. In the past, you would receive an error if you used those characters in folder or file names.
To understand this limitation, it is important to also understand what comprises a URL. There are four parts to URLS.
Protocol: http:// or https://
Server name: pitt.sharepoint.com
Folder or file path: Manager Files/New Projects/May 2015
File Name: Projections for 2016 Fiscal Year.xlsx