I am confused about links to files and folders in SharePoint Online. Especially on their robustness in case the files or folders or any of their parents are moved or renamed. The root cause of my issue is that I am unable to find any documentation on this topic. In one site I see the following kind of links. All were taken from the “…” --> “Copy link” menu. Unique document IDs are enabled.

1. 
   https://domain.sharepoint.com/:w:/r/tst/dir/[some other dirs]/file.docx?d=[some long id]&csf=1&web=1&e=[some other short id]
   From a docx file


2. 
   https://domain.sharepoint.com/:f:/r/tst/dir/[some other dirs]/testdir?csf=1&web=1&e=[some short id]
   From a folder


3. 
   https://domain.sharepoint.com/:u:/r/tst/dir/[some other dirs]/email.msg?csf=1&web=1&e=[some short id]
   From an Outlook saved email file

2 and 3 are essentially the same and no longer work if they are moved or renamed. They also stop working if any parent directory is renamed. 1 seems to work even they are renamed, moved or any of their parent directories are renamed or moved. Unfortunately, this kind of link is only available on MS Office files.

I also found another link type which is hidden in the details pane (the panel that appears if you click on the “i” in a circle on the right-hand side. In this pane the property Document ID has a link of the form

\ 4. https://domain.sharepoint.com/tst/_layouts/15/DocIdRedir.aspx?ID=[document ID]
These links are available on all files but not on folders.

They seem to continue to work on move/rename just as 1. but I found a few files that had the same ID and the link obviously does not work on those. It presents a list of search results with all the files with the same ID.

On another site I see yet another kind of link:

\ 5. https://domain.sharepoint.com/:w:/s/Website_Test/[some long id]?e=[some short id]

On this site all files including folders have the same link format. All the links to all the files and folders also survive movement and renaming including their parent folders.

Is there any documentation on the link format? I was unable to find any official documentation.

Why do the sites produce different kind of links? Is there any way to control this?

Some sites suggest that enabling unique document IDs will give links of the form 4. on “…” --> “Copy link”. Since this is not the case on my site I wonder if there is something wrong.

Why do some documents have the same ID?

Is there any recommendation to use one kind of link over the other?