This post is my summary and my conclusions on the Path Length Limit in SharePoint Online and OneDrive.

How the path length is calculated

Path Length is not the same as the URL length. It is the relative Url.

/sites/site-url/documenlibrary/folder1/folder2/filename.fileextension

Calculations rules

• Only the server relative url part is counted. The “https://[tenant].sharepoin.com” has no impact on that. It starts from the foward slash: “/sites” (or /teams).
• An encoded value such as a blankspace (%20) is treated as one character, not three.
• A unicode character, and an emoji is treated as one character. Good news for Non-English Names.
• Url Parameters, like “?Web=1” are not calculated.
• The site url and the document library url is taken into account
• All slashes are included
• A file extension is also included, and even the dot, e.g. “.docx”

Other related information

• A site url and a group name can only be 64 characters max.
• The path in the “Copy Link” is much shorter than the “real” path
• There is no limit (as of time of writing - 2019-10-30) on the folder name length (other than the bigger limit of 400 characters), I had no issues to add a folder name with 312 characters.