What Microsoft 365 Copilot can actually see in your files, and what it can't

The short version: Microsoft 365 Copilot can see exactly what the person asking can already open in SharePoint, OneDrive, email and Teams, and nothing more. It adds no access, so the risk is your existing oversharing, which it makes easy to find. At roughly NZ$35 to $52 a seat a month, the free tidy-up below is worth doing before anyone is licensed.

What it can see, and what it cannot

Content	Can Copilot use it?
Files, sites and folders the person asking can open	Yes
That person's own email, calendar, meetings and Teams chats	Yes, through Microsoft Graph
Files the person cannot open	No. Microsoft says the grounding process only reaches content the current user is authorised to access
Another person's mailbox or private OneDrive files that were never shared with them	No
Files encrypted by a sensitivity label the person has no usage rights for	No. Copilot honours the usage rights granted to the user
Documents protected with legacy Information Rights Management	Not used in Copilot grounding, per Microsoft's readiness guidance
Sites you have hidden with Restricted Content Discovery	No, although their permissions stay unchanged
Archived sites in Microsoft 365 Archive	No, until they are reactivated

Microsoft also states that prompts, responses and the data Copilot accesses are not used to train the foundation models behind it. Source: Microsoft Learn, Data, Privacy, and Security for Microsoft Copilot, Semantic indexing for Microsoft Copilot, Copilot data and compliance readiness and Get ready for Microsoft Copilot with SharePoint Advanced Management, all read on 30 September 2026.

Why old permissions become the problem

Microsoft's guidance says it plainly: Copilot operates within existing permissions, and overshared or poorly governed content can affect its results and increase risk. Before Copilot, a salary spreadsheet in a folder the whole firm could technically open was safe because nobody looked. With Copilot, "what is the office manager paid?" becomes a search that finds it in seconds.

In a firm under 20 staff the usual leaks are dull ones:

• A finance or HR folder kept in a general site that every member can open.
• Sharing links set to the whole organisation, because that was the default and it was quicker.
• A folder shared with "Everyone except external users" during a rush and never tidied.
• Broken permission inheritance on a subfolder, so it looks private and is not.
• Old sites with no owner, so nobody would ever review them.

None of these is Copilot's fault, and none is new. The permission was already there; Copilot is the first tool to make it cheap to use. The same point, for a custom agent instead of Copilot seats, is in Copilot Studio and SharePoint grounding.

Five steps before you switch it on

1. Run the Content Management Assessment. In the SharePoint admin center, Advanced Management, Start assessment. It flags potentially overshared content and ownerless or inactive sites. Microsoft suggests rerunning it every 30 days to track progress.
2. Find what is shared with everyone. The "Everyone except external users" report lists the top 100 sites where content was shared with your whole organisation in the past 28 days. The sharing links reports show which sites have the most "Anyone" and organisation-wide links.
3. Fix or lock the sensitive ones. Move HR and finance out of general sites. For a site that must stay but should not be found broadly, Restricted Access Control limits it to a named group, and Restricted Content Discovery keeps it out of Copilot and organisation-wide search while permissions stay as they are.
4. Give every site an owner and retire the dead ones. Site ownership and inactive site policies email owners, and archiving removes stale content from Copilot's reach.
5. Label what matters. Sensitivity labels classify files and can encrypt them, and Copilot respects the result. Automatic labelling and some reports need higher plans, so check which one you hold.

These tools are included once at least one person in the organisation has a Microsoft Copilot licence assigned, according to Microsoft's SharePoint Advanced Management prerequisites page; the sensitivity-label report in it needs E5. Some features, such as restricted site creation, need a separate add-on. Data loss prevention rules for Copilot, which can temporarily limit access to a document reported as overshared, are described by Microsoft as an E5 feature. In a 6 to 20 person firm the first four steps are usually a morning or two of work, my estimate, and they are worth doing whether or not you ever buy a seat.

What the licence costs

Microsoft 365 Copilot is roughly NZ$35 to $52 per user per month before GST, on top of your Microsoft 365 plan. That is a conversion of USD 20 to 30 at about 1.72, as at July 2026, not an NZD list price, and it is worked through in whether Copilot is worth it for a small NZ firm. The tidy-up above costs nothing in licences and makes every later step safer, including a decision not to buy.

When to worry less, and when to wait

• A very small firm where everyone already sees everything. If five people share all the files by choice, Copilot changes little. The sites to check are payroll, personal files and anything about clients under a confidentiality term.
• You have not looked at sharing since the tenant was set up. Wait to license anyone until you have run the assessment and read the two sharing reports.
• Your data is mostly outside Microsoft 365. Copilot sees what is in Microsoft 365; a database on a server is not in its reach unless someone connects it. See Copilot against a Copilot Studio agent.

Common questions

Wondering what Copilot would find in your files?

Tell me roughly how your SharePoint is laid out. One free 30-minute call and I will say what to check first and whether seats are worth buying yet.