Azure ACS retirement. How to prepare your tenant. Guide for SharePoint Admins.

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Since Microsoft announced EOL of ACS in 2026, we as SharePoint administrators must be prepared, as it is a really big deal – entire era of SharePoint app-only service principals will gone. SharePoint developers used this kind of authentication since 2013 to build their solutions. And when it comes to software development – it always takes time. Imaging all the code that was designed since 2013 needs to be reviewed and re-written to adopt changes. So it is critical that we should take measures now to avoid huge problems in April 2026.

Recommended transition tactics

For developers

  • Prioritizing using Microsoft Graph API.
  • In cases Graph API does not provide required functionality – it’s ok to use SharePoint API, but please ensure certificate is used (not secret).

For SharePoint admins

High-level recommended steps are:

  • Encourage users registering applications in Azure (not in SharePoint)
  • Disable ability for site owners register service principals in SharePoint via appregnew.aspx
    Your users will start seeing “Your SharePoint tenant admin doesn’t allow site collection admins…” message (see details), but that’s ok.
  • Create a process so users can request permissions to SharePoint sites for their Azure-Registered Apps. Provide Sites.Selected permissions by default. Consider automation.
    In rare cases when 3-rd party apps require legacy ACS-based permissions, it would be you (SharePoint service admin) who will provide ACS-based access to sites.
    Track this activity (so you know for whom this ACS-based permissions were provided).
    Inform every developer that ACS will be gone.
  • Keep audit logs
    Starting today and until it’s over you’d get audit logs from Microsoft 365 purview center – consider selecting all events anyone visited appinv.aspx page.
  • In March-April 2025 (1 year before) ACS EOL, start notifying developers who use ACS.
    You can get list of developers combining
    – audit log data
    – report from Entra Id on apps owners
  • In advance ( let say, starting September 2025) you can try to temporary switch off ACS (“scream test”).

Detailed steps:

Encourage users registering applications in Azure (not in SharePoint)

Pro’s for App Registered in Entra Id (vs SharePoint Apps-only service principals – apps registered in SharePoint with AppRegNew.aspx) :

  • Support authentication with client secret and/or certificate, custom expiration time
  • Support both – classic SharePoint REST API and CSOM and Microsoft Graph API

Disable registering service principals in SharePoint

Disable ability for site owners register service principals in SharePoint via appregnew.aspx with Set-SPOTenant PowerShell cmdlet

Set-SPOTenant -SiteOwnerManageLegacyServicePrincipalEnabled $false
When the value is set to false, the service principal can only be created or updated by the SharePoint tenant admin. Your users will start seeing “Your SharePoint tenant admin doesn’t allow site collection admins…” message (see details), but that’s ok.

tbc

References

Using metadata to refine your SharePoint search

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Though search in Microsoft 365 SharePoint is good out-of-the box and you can do a full-text search and refine your results by “File type” and “Last modified”, but what if you want your content be tagged with your custom metadata (e.g. “Article category”), and you want to be able to refine your search results based on this metadata? I’d say it is possible and I’ll provide the solution below. The solution includes working with site term store (creating terms, term groups, term sets), configuring list/library columns and updating site search schema (mapping crawled properties to managed properties).

PowerShell Script for Files Deduplication

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If you think you have a lot of duplicated files that consumes your hard drive storage space, this article is for you. Personally, I have a lot of video and pictures on my working hard drive and on a backup HDD. While working with photos and videos I can rename files, copy or move them from folders to folders. As a result, I end up with gigabytes and terabytes occupied with duplicated files. So I need a tool to a) find duplicated files and b) remove duplications. I tried to find good scripts but somehow I was not happy with what I found, so I wrote scripts myself.

Surely you can buy/try a 3-rd party toot with GUI, but if you are comfortable with PowerShell – consider the following.

…

References

Birds of Eurasia Best Pictures

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There is a new site – Birds of Eurasia Best Pictures – with a lot of good pictures of birds from all of the Eurasian continent. It does not seem that pictures are professional, sooner shots are made by amature birdwatchers, but some pictures are really nice.

Pictures are updated around weekly. Here is an example:

Cinereous Vulture (Aegypius monachus)

Shoot in Mongolia by Oleg Belyalov

Another great picture:

Collared Pratincole by Philippe Campeau, Kyrgyzstan

Collared Pratincole by Philippe Campeau, Kyrgyzstan

References

Restricted SharePoint Search Deep Dive

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Restricted SharePoint Search is a new Microsoft feature to mitigate sites oversharing issue when you are implementing Copilot. The feature is documented here, but still I have some questions, e.g.:

  • How about external data? Copilot can use external data to learn from via agents and connectors. But would Restricted SharePoint Search if implemented allow data from external connectors to be used in copilot?
  • “Users’ OneDrive files, chats, emails, calendars they have access to” – means own data for every single user or all shared OD data?
  • What exactly is “Files from their frequently visited SharePoint sites”? I mean, how frequently user needs to visit site for this?
  • What exactly means “Files that the users viewed, edited, or created.”
  • What about teams chat messages, e-mails, viva engage messages?
  • “Files that were shared directly with the users” – does that mean “individual files shared” or can include folders, libraries, sites?
  • If user is a member of a teams – would all team content included?
  • It says “Files…” but would site pages be included? Or list items? Or list items attachments? Pages is something that people use to create wiki to share knowledge.
  • How long it takes for Microsoft 365 to start restricting results after Restricted SharePoint Search is enabled
  • How to deal with “You do not have the required license to perform this operation” when you are trying Get-SPOTenantRestrictedSearchMode or Get-PnPTenantRestrictedSearchMode

Here I’m going to answer the questions above.

So far I build a test scenario using my dev tenant that includes multiple collaborated users and content in the form of files, pages, list items and messages spreaded across multiple sites falling into different categories of Restricted SharePoint Search allowed content.

WIP (Work in progress)

References

SharePoint Governance

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Governance in IT is establishing rules, policies, tools and practices that helps you manage and protect your enterprise resources. SharePoint governance (or wider – Collaboration governance) covers

  • resources ownership and lifecycle
  • users’ access to resources
  • compliance with your business standards
  • security of your data

References