Restore permissions inheritance for the targeted locations.
You can restore inheritance at several levels, including for sites, lists, libraries, folders, or documents.
Index
Prerequisite(s)
You have site collection admin permissions on your targeted site collection(s).
Note: Site collection admin permissions are required even if you have higher admin privileges like SharePoint admin or Global admin permissions. For more information, see Microsoft administrative permissions.
Tip: To manage all your site collections, you can connect to your central admin or admin center with SharePoint admin, Farm admin or Global admin permissions.
How-to
Select Explore from the sidebar.
Navigate to the target you would like to restore inheritance for.
Select the target(s).
Click Restore inheritance in the Quick actions menu.
Select an option under What would you like to do with the permission inheritance? (Details on each option can be found below.)
Click Restore.
Once the action is complete, you will see a report with the results (successes, errors, and warnings). In the case that there are warnings or errors, they will be displayed with details in separate tabs near Results. Click Export to download a record of the task as an XLSX or CSV file.
Permission inheritance options
You can select one of the following options to restore the permissions inheritance on your items:
Restore only for the selected targets
This will restore the permission inheritance on the selected targets. For instance, running this option on multiple libraries will restore the permission inheritance of the selected libraries, but it will not remove all the custom permissions on the documents within the selected libraries.
Restore for the selected targets and all their children recursively
This will restore the permission inheritance of the selected targets and all the items within the targets. For example, using this option on a site removes every single custom permission from that site.
Note: This operation cannot be undone.