Durable Links is a fancy name for a functionality that solves a problem.
Back when we were using file shares to store documents, the path to a certain document looked something like:
Whenever we sent a link to that document in an email or referred to it in another document, that’s the link we used. One of the weaknesses was that whenever we renamed the file to something else or changed it to a different folder, that link would break.
After we convinced our users to move their documents to SharePoint, the problem improved ... but did not disappear. In SharePoint, the path looked like:
If the document was renamed or moved to another document library, that link would still be broken.
That is what the new Durable Links feature in SharePoint Server 2016 is trying to fix. Durable Links is dependent on Office Online Server (the new Office Web Apps), which, despite the “online” name, is fully on-premises. After linking Office Online Server with SharePoint Server 2016, all the documents that can be opened by default with Office Online Server will have an ID added at the end of the URL.
As you see, the first part of the URL is still Path Based. If we move that document to another document library and rename it to Proposal, the new link would look like:
The first of the URL that is path based will change to show the new path and document name, however the ID behind d=stayed the same.
Whenever a user navigates to the old URL, SharePoint will automatically redirect the user to the document location, which will then open in Office Online. Here is a diagram from Microsoft that explains a bit more how the whole process works.
Image Source: Microsoft
As we said before, this works with all the documents that can be opened with Office Online Server out of the box, so Word, Excel, PowerPoint, OneNote and PDF.