Redact a PowerPoint before AI sees it

To redact a PowerPoint for ChatGPT, Claude or Copilot, start from a duplicate of the deck and remove people from the file itself, not only from view. Unhide every hidden slide, read and then delete the speaker notes and comments, open the slide master, and paste each chart back as a picture so that its Excel workbook stays behind. Then replace the names left on the slides, and let Inspect Document make a last sweep before anything is uploaded.

A black rectangle laid across a name, white lettering on a white slide or a text box dragged past the edge changes what an audience sees. Software reading the .pptx gets the words regardless.

The guide is for UK offices that want an AI assistant to tighten a deck, summarise a meeting pack or turn slides into a report. Menus follow Microsoft’s UK support pages, in PowerPoint for Windows unless we say otherwise. What each provider keeps after an upload is answered in how long OpenAI holds on to ChatGPT conversations and which Copilot is safe for client work.

How to redact a PowerPoint: the order to work in

A presentation spreads what it knows across more places than a letter does, and the sequence matters. Replace a surname on the visible slides before you unhide the rest, and the hidden slide keeps it. Delete the notes before reading them, and you lose the one place that told you who else is involved. Seven steps, which the sections below take one at a time:

1. Duplicate the deck. Call the duplicate something nobody could confuse with the version you present from, and make every change there.
2. Bring back what is hidden. Unhide every hidden slide and look past the edge of each one.
3. Read the notes, then delete them. Speaker notes are usually the most personal text in a deck.
4. Clear the comments. Resolved threads included, because resolving a thread does not delete it.
5. Open the slide master. Anything typed there appears on every slide and cannot be clicked in the normal view.
6. Flatten the charts. Paste each chart back as a picture, so that the workbook inside it stays behind.
7. Replace, then inspect. Swap the names still on the slides for codes, run Inspect Document, and read the copy once more.

Whether the firm allows the tool at all comes before any of this, and a written policy naming the AI tools staff may use settles it. For which details are personal data to begin with, see the British identifiers worth removing, from NI numbers to case references.

What a .pptx holds that the audience never sees

A PowerPoint file is a compressed archive of separate parts. Microsoft’s page on Open XML formats explains that a .pptx is stored with zip compression and that its components are kept separate from each other: one part per slide, one per page of notes, others for comments, the slide master, each chart and the file’s properties. A slide show draws on some of those parts. An upload sends every one of them.

To see this in a real file, we put together a short client review deck from invented details: four slides, one of them hidden, a page of speaker notes, two comments, a chart, a text box dragged off the first slide, and a picture description for screen readers. Then we opened it as the archive it is and listed the text inside each of its 39 parts, with a small script and no PowerPoint.

39parts inside the .pptx

10people named inside the file

4of them on screen during the slide show

6only in parts the show never displays

Six of the ten people never appeared on a projected slide, and each of them was a click or two away for anyone who opened the file.

How each AI assistant treats each of those parts is something we have not tested, so we make no claim about it. Microsoft describes Copilot in PowerPoint as able to read through the presentation and summarise it, without listing which parts it reads. The ICO’s disclosure guidance points to the safe assumption: anything stored in a document leaves with it.

A hidden slide is still in the deck

Microsoft’s page on hiding a slide puts it in one line: a hidden slide remains in the file, and it is merely hidden when you run the slide show. In the thumbnail pane it shows a slash through its number. Microsoft’s own reason for hiding slides is to keep different levels of detail for different audiences, which is exactly why hidden slides collect the material a client was not meant to see.

Ours was titled “Not for the client” and held a second contact’s name and mobile number. To bring one back, select its thumbnail, right click and choose Unhide Slide. In the copy for the AI, then decide whether the slide belongs there at all; if it does not, delete it rather than hiding it again.

Text parked off the edge of the slide

PowerPoint lets you drag anything into the grey area around a slide, where it stays with the file but never appears in the show. Microsoft’s Inspect Document page calls this off slide content: text boxes, clip art, graphics and tables moved outside the slide area. The ICO lists moving information to the fringes of a document among the techniques that do not keep it secure.

In our deck, a reminder to ask a named man about his divorce settlement sat just past the right edge of the first slide. Zoom out in Normal view and it is plain to see. Microsoft adds a catch worth knowing: Inspect Document does not detect or remove off slide objects that carry animation effects, so look for yourself as well.

Descriptions written for screen readers

Alternative text is the description a screen reader speaks aloud for a picture, chart or shape, and Microsoft’s page on adding alt text shows where to write it: right click the object and choose View Alt Text. A team photo on a slide tends to get a description with everyone’s name in it. In our deck, “Photo of” followed by the full name of someone on the slides travelled as plain text inside the shape.

Here are all seven places we used, and how to reach each one in PowerPoint:

Where we put it	Where it sat in the file	Who it named	To find it in PowerPoint
A hidden slide	Its own slide part, marked not to show	A second contact, with a mobile	Right click the thumbnail, Unhide Slide
Speaker notes	A notes part for slide 2	Whoever referred the client	View, Notes Page
Text box off the slide	Slide 1, past its right edge	A name, and a note about a divorce	Selection pane
Two comments	Comment parts and an author list	Five people, two as authors	Review, Show Comments
The chart	An Excel workbook inside the deck	A referrer the chart never draws	Chart Design, Edit Data
A picture description	A property of the shape	Someone already on a slide	Right click, View Alt Text
File properties	Two properties parts	The colleague who built the deck	File, Info

Sources: our test .pptx, generated by script from invented details, parts listed without PowerPoint; Microsoft Support pages on hiding slides, speaker notes, comments, charts, alt text and Inspect Document.

Do not simply delete alt text, because the deck still has to make sense to someone who cannot see it. Rewrite it to describe the picture without naming anyone. If the photo itself shows people who should not reach the AI tool, the photo has to go from the copy as well. A face or a job title can point to one person with no name attached, as our page on pseudonymised client files explains.

Speaker notes, the script written for one reader

Microsoft’s page on speaker notes describes the Notes pane as the place for talking points, visible on the presenter’s monitor and not to the audience. That is why people write in them what they would never put on a slide: who referred the client, a mobile number to ring before the meeting, the awkward line about fees, the colleague who is leaving.

Microsoft’s Inspect Document page says the same thing more plainly: the notes can contain text you might not want to share, especially if they were written only for the person delivering the presentation. In our test deck, the notes named the person who had referred the client and gave her mobile number. Neither appeared anywhere a room would see.

Reading every note before you delete any

Before removing anything, read the notes as a whole. PowerPoint can send them to Word in one go: File, Export, Create Handouts, then choose Notes below slides, as Microsoft’s page on printing speaker notes describes. You get one document with every slide and its notes, which is quicker to read than clicking through Notes Page view one slide at a time.

That document is also a record of what the presenter meant to say, so file it with the matter rather than in the folder you upload from. If the AI actually needs the talking points, to turn them into a script or a handout, clean them the way you would clean any Word file, as in redacting a Word document step by step.

Removing them all in one go

To clear every note from the copy, run Inspect Document, tick Presentation Notes and press Remove All. Microsoft’s page is precise about the limits: it removes the text added to the Notes section, but it cannot remove pictures added there, and what it removes may not come back with Undo. A screenshot pasted into the notes has to be deleted by hand.

Most of what you find when you search for how to remove speaker notes from PowerPoint is written for sharing a deck by email or on a video call, and the method is the same here. The difference is that for an AI tool, the notes are often the part worth keeping, which is why reading them first matters more than deleting them fast.

Review comments, and who wrote each one

Comments are the conversation around a deck: who to check with before it goes out, whose email address has changed. Microsoft’s Inspect Document page notes that comments let other people see the names of those who worked on the presentation along with what reviewers said, and its comments page adds that comments are stored in the file itself.

In our test deck, two short comments named three people and carried the names of two colleagues as their authors: five people in all. None of that appears on a slide. All of it travels with the .pptx, and all of it is readable by anything that opens the comment parts of the file. Word files carry their comments the same way, and removing comments and tracked changes in Word needs a routine of its own.

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Classic and modern comments

PowerPoint has two kinds. Microsoft’s page on modern comments explains that they are on by default for enterprise customers, and that a file which already had older comments keeps the older kind. The detail that matters for redaction is on the same page: a resolved thread no longer appears in the margin, but you can still find it in the Comments pane. Resolving is tidying up, not deleting.

To delete a thread, select it in the Comments pane, open More thread actions and choose Delete thread. To delete every comment at once, run Inspect Document with Comments ticked and press Remove All. The name on the deck itself, as author or last saved by, is a file property, which the Inspector’s document properties check clears; for the Word and PDF side of that layer, see what a file’s properties give away.

The slide master: text on every slide that you cannot click

Every deck is built on a slide master, the template that sets fonts, logos and anything else meant to repeat. Microsoft’s page on the slide master opens it from View, Slide Master, and explains that if you cannot edit something on a slide in Normal view, it may be because it is defined on the master or on one of its layouts.

That is where a line such as “Confidential: prepared for” followed by the client’s name tends to live in a pitch or review deck. In ours it sat on the master and appeared on every slide, and clicking it in Normal view did nothing. The same goes for a client logo or a matter name added to a layout.

Open Slide Master view, click through the master and each layout under it, and edit the text there. Footers deserve the same look. Our deck carried the client’s surname in the footer of every slide, which in a long deck is a name repeated thirty or forty times. Estate agents building vendor pitches and accountants preparing client reviews both use this kind of branded template; there are pages for estate agents and accountants that go further.

Charts that bring their own Excel workbook

A chart in PowerPoint is rarely just a picture. Microsoft’s page on copying from Excel to another Office program lists the ways a chart can arrive on a slide: with its workbook embedded, linked to the workbook it came from, or as a picture. Only the last carries nothing but the image.

Embedding is the one to watch. Microsoft’s page on inserting Excel data in PowerPoint warns that embedding may give more access to your Excel file than you intend. In our test deck, the chart drew two clients’ fees. The workbook inside it had a third column the chart never used, naming the person who had referred one of them.

How the chart was pasted	What the .pptx carries	For the copy you send
Embed workbook	A copy of the workbook	Replace it with a picture
Link data	A tie to the source workbook	Replace it with a picture
Picture	The image and nothing more	Keep it

Sources: Microsoft Support, Copy from Excel to another Office program; Insert and update Excel data in PowerPoint. The right hand column is our suggestion.

Paste the chart back as a picture

Microsoft’s page on embedded files or objects gives the route for keeping a chart while dropping its data: select the chart area and press Ctrl+C, press Ctrl+Alt+V where the picture should go and pick a picture format, then select the original chart and delete it. The ICO’s disclosure guidance proposes the same move, using Paste Special.

A pasted picture cannot be edited, which is fine in a copy meant for an AI tool. If the task needs the figures themselves, type the few numbers it needs onto the slide as text, and leave the rest of the workbook out.

Linked charts and the file they point to

A linked chart keeps a tie to the workbook it came from, and Microsoft notes that to unlink it you copy it and paste it again, embedded or as a picture. For the AI copy, a picture is the answer again.

The workbook at the other end of the link, or the one you copied the chart from, is its own document with its own hiding places, from hidden sheets to pivot table caches. Our Excel redaction guide goes through them. And if a deck has already gone out with a referrer’s name inside its chart, the breach rules for client data sent to AI say what to weigh next.

Covering a name on a slide leaves it in the file

Slides invite visual tricks, because a finished slide looks like a printed page and drawing on it feels like enough. The ICO’s page on hidden personal information in documents, published on 31 July 2025, names four that fail: text or background recoloured until the words vanish, objects laid over information, information moved to the fringes, and invisible formatting.

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Fill a rectangle black and lay it across a name in a table, and the slide now holds two things: the table, with the name intact, and a shape above it. Anything that reads the slide receives the name as ordinary text. Microsoft’s Inspect Document page adds that the Inspector does not detect objects covered by other objects, so this is a trap the built in check will not catch for you.

Screenshots are the same problem in picture form. A black box over part of a pasted screenshot leaves the whole screenshot underneath. Cropping is not deletion either: Microsoft’s page on reducing the size of a picture offers a separate Delete cropped areas of pictures check box under Compress Pictures, which only makes sense if the cropped part is still stored.

The Selection pane lists what is covered

The quickest way to find what sits under something else is the Selection pane. Microsoft’s page on the Selection pane opens it from Home, Select, Selection Pane, or with Alt+F10. It lists every object on the slide, top ones first, and lets you hide each in turn to see what lies underneath.

When you find a covered name, delete the covering shape and then deal with the text itself: delete it, or replace it as in the next section. For a screenshot, take a fresh one without the details and swap it in. PDFs have their own version of the covering trap, dealt with in redacting a PDF so it stays redacted.

Replacing names on the slides themselves

Once everything hidden is back in view, the names on the ordinary slides are the last layer. Microsoft’s page on finding and replacing text in PowerPoint gives the route: Home, then Find and Replace in the Editing group, with Find Next to check each hit and Replace All once you are sure.

Give each person a label that keeps the sense, such as Client A and Referrer B, rather than one blank marker for everyone. An AI tidying an actions slide has to tell the one sending the accounts from the one booking the meeting. Start with each surname alone, then first names, initials and email addresses, because a deck rarely spells a name the same way twice.

Keep the key somewhere else

Store the key, the list matching labels to people, in its own file on the firm’s systems, never on a hidden slide of the same deck. Labelled data remains personal data for whoever can match it back to people, as the ICO sets out in its guidance on pseudonymisation, which is why the key has to sit apart and under lock.

Read tables and SmartArt diagrams slowly. In our file the words of a SmartArt diagram sat in a part of their own, apart from the slide, and an organisation chart built that way is a list of names.

Minimisation under UK GDPR, Article 5(1)(c) is the rule behind all of this: send only what the job needs. Training decks for HR can also carry sickness or disciplinary details, where the extra rules for health and other sensitive data apply on top.

Inspect Document in PowerPoint, and the gaps in its list

Inspect Document is Microsoft’s built in check. With the duplicate open, choose Info on the File tab, then Inspect Document under Check for Issues. Pick the categories to search, press Inspect, use Remove All on whatever should not travel, and Reinspect to confirm. Microsoft advises running it only on a copy, and adds that from then on PowerPoint strips personal information at every save, until you change that setting.

What matters for redaction is what each inspector covers, taken from Microsoft’s own list for presentations:

Content	What Inspect Document does
Comments and ink	Finds and removes
Document properties	Finds and removes
Presentation notes	Removes the text, not pictures
Content off the slide	Removes it, unless it is animated
Invisible objects	Removes them, not objects covered by others
Embedded workbooks and objects	Reports them, leaves them to you
Hidden slides, master text, alt text	Not on its list

Source: Microsoft’s Inspect Document page, PowerPoint section. The last row is our reading of what that list leaves out.

Hidden slides are not on it

The Inspector’s PowerPoint list covers comments, properties, invisible and off slide content, notes and custom XML. A hidden slide is none of those: it is a whole slide that the show skips, so a clean result tells you nothing about it. The same goes for the slide master, alternative text and every name typed in plain view, which is why the first six steps come before this one.

The ICO says as much about any tool of this kind: use it, and then check the document yourself as well.

A PDF of the deck is a different upload

Saving the deck as a PDF first does not settle the question. Microsoft’s page on saving presentations as PDF shows options to include hidden slides, comments, ink and document properties, or to publish notes pages instead of slides, and in the ICO’s words a PDF conversion does not display everything a document holds. Clean the .pptx first, export second, and check the result as described in our PDF redaction guide.

A client review deck through Nonimo

Pick the .pptx in the Finder on a Mac or in File Explorer on Windows, then press your Nonimo key. What lands on the clipboard is the text of the slides, hidden ones too, plus the speaker notes, with personal details covered, ready for the chat; paste the reply back and the names return. That route gives you text; drop the .pptx onto Nonimo’s window instead and you can also download a covered copy as a PowerPoint file, with the save dialog opening in the original’s folder on a Mac. Working from an older .ppt? Save it as .pptx first and Nonimo takes it from there.

Our invented deck: a client slide, an actions table, hidden slide 3, notes on slide 2. The file, then the clipboard from Nonimo, exactly as printed:

Reading the file (slide 3 is hidden; the last two lines are the notes)
Quarterly client review
Client: Ottoline Varcoe
Email: o.varcoe@example.com

Actions agreed
Name	Mobile	Email	Action
Fenella Garstang	07700 900462		Send the draft accounts
Amara Boateng		a.boateng@example.com	Book the October meeting

Not for the client
Name: Marigold Oakhurst
Phone: 07700 900318

Referred by: Adaeze Hartley
Mobile: 07700 900787

On the clipboard from Nonimo
Quarterly client review
Client: [PERSON_1]
Email: [EMAIL_1]

Actions agreed
Name	Mobile	Email	Action
[PERSON_2]	[PHONE_1]		Send the draft accounts
[PERSON_3]		[EMAIL_2]	Book the October meeting

Not for the client
Name: [PERSON_4]
Phone: [PHONE_2]

Referred by: [PERSON_5]
Mobile: [PHONE_3]

The actions stay for the AI. Give the clipboard a quick read before pasting. What Nonimo stores and sends is on the security page.

Sources

• How do we avoid an accidental breach when personal information is ‘hidden’ in documents?, ICO, part of Disclosing documents to the public securely, 31 July 2025: the four ineffective techniques (text or background colour, covering with objects, moving information to the fringes, invisible formatting); keeping a picture of an embedded chart through Paste Special; converting to PDF does not display all the information; checking documents yourself even after a software tool.
• Remove hidden data and personal information by inspecting documents, presentations, or workbooks, Microsoft Support: File, Info, Check for Issues, Inspect Document; the PowerPoint inspectors and their limits (notes pictures, animated off slide objects, covered objects); embedded objects found but not removed; use a copy; automatic removal of personal information on later saves.
• Open XML Formats and file name extensions, Microsoft Support: .pptx files use zip compression and keep their data components separate.
• Hide or show a slide, Microsoft Support: a hidden slide remains in the file and is only hidden in Slide Show view; Unhide Slide; hiding slides for different audiences.
• Add speaker notes to your slides, Microsoft Support: notes are visible to the presenter and not to the audience.
• Print speaker notes, Microsoft Support: File, Export, Create Handouts, Notes below slides, to open the notes in Word.
• Add, change, hide, or delete comments in a presentation, Microsoft Support: comments are stored in the file; More thread actions, Delete thread.
• Modern comments in PowerPoint, Microsoft Support: on by default for enterprise customers; files with older comments keep them; resolved threads leave the margin but stay in the Comments pane.
• What is a slide master in PowerPoint?, Microsoft Support: View, Slide Master; items you cannot edit in Normal view may be defined on the master or a layout.
• Copy from Excel to another Office program, Microsoft Support: embedded, linked and picture paste options for charts; unlinking by pasting again.
• Insert and update Excel data in PowerPoint, Microsoft Support: embedding may give more access to your Excel file than you intend.
• Embedded files or objects found, Microsoft Support: an embedded Excel chart can hold data you only see in Excel; Ctrl+C, Ctrl+Alt+V, picture format, delete the original.
• Add alternative text to a shape, picture, chart, SmartArt graphic, or other object, Microsoft Support: what alt text is for; right click, View Alt Text.
• Use the Selection pane to manage objects in documents, Microsoft Support: Home, Select, Selection Pane, or Alt+F10; overlapping objects listed top first; show or hide each one.
• Reduce the file size of a picture in Microsoft Office, Microsoft Support: the Delete cropped areas of pictures option under Compress Pictures.
• Find and replace text, Microsoft Support: Home, Editing, Find and Replace; Find Next, Replace, Replace All.
• Save PowerPoint presentations as PDF files, Microsoft Support: PDF options for hidden slides, comments, ink, document properties and notes pages; fewer options in PowerPoint for macOS.
• Summarize your presentation with Copilot in PowerPoint, Microsoft Support: Copilot can read through the presentation and give a bulleted summary.
• Pseudonymisation, ICO: pseudonymised data is personal data for whoever holds the additional information, which must be kept separately and securely.
• UK GDPR Article 5, legislation.gov.uk: data minimisation, Article 5(1)(c).