SharePoint Online REST API - searching with external user

Question

In my application, I'm getting the list of all sites with this search API call:

/_api/search/query?querytext='contentclass:STS_Site'

However, it does not work for external users, despite having all permissions for certain sites. (It does not work either if external users have access to all sites.) This is the response:

{"error":{"code":"-2147024891, System.UnauthorizedAccessException","message":{"lang":"en-US","value":"Attempted to perform an unauthorized operation."}}

Is there a way to enable searching for external users? (I'd expect the call lists only the sites the user has access to.)

Answer 1

The default search results page for team sites (osssearchresults.aspx) does not allow external users to see any results, to enable search for external users, we can enable external access to search center and share the search center to external users, then configure team site to use search center instead of default search results page.

The search has security trimming feature which the search results can only be viewed by users who have access to the items. In the content Search web part, the external users can view the results which a user shared the content to external users including other site collections which give access to external users.

Besides, you can add a sourceid of a result source you created to your REST seach api url to let external users to view the results. Reference:

Searching for site content shared with external users

Office 365 SharePoint Search for External Users