Posted by Microsoft keeps improving the way we can share our information in SharePoint Online. And in this case: external sharing.
External sharing means: sharing with people who do not have an account to access your SharePoint Online environment. Some might call this anonymous access.
Using the administration interface of Office 365 you can enable or disable this option. But this is high level. When enabled, this option allows your people to share sites and items. There are some considerations here. What are people allowed to share and is there a need to request permission before the site or item is shared? These all depend on the site-permissions combined with the Access Request Settings of the site. I won’t go into these in detail here.
But Microsoft just added another option to this functionality. Until now, you could share an item to an external user or anonymous user using a link. But you needed to disable this link yourself, when needed. Now it is possible to set an expiration period for this link.
How cool is this?
Just share a document with someone for one day, for example.
Information security and compliance 
Hi Albert,
Is there a way to retrieve this info via REST APIs? Info like, when is the link going to expire (given the link in the request) OR whether or not the global settings has the external sharing on/off.
Hi Mo,
Sorry for the late reply.
I’m no designer so I’m not really an expert on this.
But I do know that the Office 365 audit log can be connected to using API’s and there’s also some external sharing API’s.
Here’s more information:
https://blogs.msdn.microsoft.com/vesku/2015/10/02/external-sharing-api-for-sharepoint-and-onedrive-for-business/
https://docs.microsoft.com/en-us/office/office-365-management-api/office-365-management-activity-api-reference
Hi Albert, is there a way to set a default expiration on the sharing link, to e.g. 2 months?
Hi Paul,
To my knowledge this is only possible when your sharing using anonymous links. Then the person sharing the link can set an expiration date. You can set a default expiration period (in days) in the SharePoint admin (classic mode – Sharing section).
Using anonymous links is only suiteble in specific scenario’s. So only use it with specific site(collections).
You can also set an expiration date on content (not the link) when using information rights management. The content is encrypted on download and after the expiration date, it cannot be opened.
The default sharing link for external users (using an access-code) is only valid for 15 minutes, by the way.
Hope this helps?
Al
Now there is a new concept of creating “Shareable Links” using Microsoft Flow:
Use Microsoft Flow to generate tenant-shareable links for SharePoint Online
The article highlights a use case for a SharePoint document library, however, there are actions that perform the same functionality on OneDrive for Business (preview) as well.
This method even supports configuration of an expiration date.