· Updated · Written and maintained by Nonimo
You redact in Word by deleting or replacing the words themselves, not by covering them. Black highlighting, white text and the No Markup view change what the page shows; the characters stay in the file, and a tool that reads the file can read them. So the method is a sequence: replace every mention, accept or reject every tracked change, delete every comment, remove hidden text, and only then open the corners Word keeps apart from the main text.
A .docx you upload to an AI assistant is read as a file, and Claude’s help center, for one, lists DOCX among the formats it takes. What that reader sees depends on how the file is opened, and we found no provider documentation saying which parts of a .docx its reader leaves out.
This guide stays inside Word, with the menus of Word for Microsoft 365 on Windows as Microsoft documents them. The PDF, the document properties and the list of identifiers to take out are subjects of their own. If your question is what redaction does for privilege rather than how to do it, that is a separate guide on US rules.
How to redact in Word: the order that works
Redaction in Word is done with tools built for editing, and each one covers part of the job. The order below removes whole layers first, so that your search for names later runs through less material.
- Save a copy. Every step below is destructive, and some cannot be undone.
- Settle the tracked changes. Accept or reject each one, or all of them at once, so the file holds one version of the text.
- Delete the comments. All of them, from the Review tab, not just the ones you can see.
- Show and remove hidden text. Turn on the display of hidden text and delete what it reveals.
- Replace names and numbers. Use Replace one hit at a time, then search again for every variant.
- Open the rooms outside the body. Headers, footers, footnotes, text boxes, fields and embedded objects each need a look of their own.
- Inspect the document. Run the Document Inspector as a last net, then read the result as a stranger would.
The sections below take the steps in turn, with what each catches and what slips past it. A firm that wants them written into its rules can start from our editable AI policy.
A black highlight is formatting, and the words are still in the file
Most failed redactions in Word are a good instinct and the wrong tool. You want the Social Security number gone, so you make it disappear: black highlight and black font, or white font on a white page. On screen the job looks done. In the file, nothing has been removed, because color is an instruction about how to draw the characters, not a change to the characters.
A .docx is a zip archive of separate parts. The body, the header, the footnotes and the comments are stored apart, and a program that opens the file can read each part whether or not Word shows it. A PowerPoint file is packed the same way, so its presenter notes and chart workbooks ride along too.
What we put in our test file
Rather than take this on faith, we wrote a short test memo by hand, every detail invented: a client called Dolores Vantreight, a made up SSN, 000-58-1427, a 555 phone number and an example.com email. Then we hid things the way people do: a black highlight over the SSN, a tracked deletion of her address, a tracked insertion of a settlement figure, a comment, a hidden line, a header, a footnote and a text box.
Three programs, three different texts
Then we asked three ordinary programs to pull the text out: python-docx, the library a great many scripts use, the textutil converter that ships with macOS, and LibreOffice saving to plain text. We did not test what any AI provider does inside, because none documents it. What happens to an upload afterward is a question of terms, which we have read for ChatGPT and Claude.
| What we hid in the test memo | python-docx | macOS textutil | LibreOffice |
|---|---|---|---|
| SSN under a black highlight | Returned | Returned | Returned |
| Line formatted as hidden | Returned | Returned | Returned |
| Tracked insertion | Not returned | Returned | Returned |
| Tracked deletion (her address) | Not returned | Not returned | Returned |
| Text box | Not returned | Returned | Not returned |
| Footnote, header, comment | Not returned | Not returned | Not returned |
Every program returned the highlighted SSN and the hidden line. One returned a street address that Word, in its final view, would not have shown at all. The empty rows are no comfort either: the header, footnote and comment were still in their own parts of the archive, readable by any program that looks there. You cannot redact for one reader. You have to empty the file.
Tracked changes and comments, before you redact
Before you touch the names, accept or reject every tracked change on your copy and delete every comment: the No Markup view only hides changes, and a comment keeps its author’s name. In our test memo, one extractor returned a tracked deletion of the client’s address, and none returned the comment, still stored in its own part of the file. Removing track changes in Word, comments included has every menu for Windows, Mac and the web.
Saving the copy in another format does not get around this, since an RTF file still carries tracked changes.
Hidden text and white text, two kinds of invisible
Word has a font effect called Hidden. Text formatted with it stays in the document, and Word only displays or prints it if you change its display and print options. In our test memo it held one line: the client’s daughter, named, as a witness. Excel’s version is the hidden row, column or sheet, and a program that opens the workbook reads those just the same.
That line came back from all three extractors. It is the clearest case in the test of a detail that a reader of the page would never see and a reader of the file would always get. If a file like that has already been uploaded, the next question is whether a paste of client data counts as a breach.
How to make it show up
Go to File > Options > Display and select Hidden text. Microsoft describes the result as a dotted line under text that is formatted as hidden. You can also search for it: open the Navigation Pane from the View tab, select the magnifying glass, then Settings and Advanced Find & Replace, and use the Format menu to look for the Hidden font effect. Once you can see the text, select it and delete it.
White text is a different problem
White text on a white page is not hidden in Word’s sense, so the options above will not reveal it. The Southern District of Alabama’s redaction guidance makes the point about this exact method: changing the font to white makes the words look as if they disappear, but they do not. Microsoft adds that its Document Inspector cannot detect text hidden this way.
On a copy, selecting everything and setting the font color back to Automatic is a quick way to make it visible.
Find and Replace, and the mentions it walks past
Replacing is the real redaction step in Word, and it fails quietly. Go to Home > Editing > Replace, type the name in Find what, and type a placeholder such as [CLIENT] in Replace with. Microsoft itself suggests stepping through the hits one at a time with Replace, and for redaction that is the only sane way: Replace All changes things you never looked at.
The deeper problem is that Replace finds a string, and people are not written as one string. In our test memo, the client and her family were named in nine places. A search for her full name, exactly as it appears in the case caption, matched two of them.
The variants that break a search
The other seven were ordinary writing. There was the surname on its own in the caption, a possessive, the first name alone in a to do line and in the text box, the surname in capitals in the header, her daughter’s name, and the email handle, where the surname is glued to an initial. None of these is unusual. Most documents about a person are full of them.
| Written as | Why the full name search misses it | Search for |
|---|---|---|
| Ms. Vantreight’s supervisor | Surname without the first name | The surname alone |
| draft the letter for Dolores | First name without the surname | The first name alone |
| File: VANTREIGHT, D. | Surname first, then an initial | The surname, then read each hit |
| dvantreight@example.com | Name inside an email address | The surname without whole words only |
| Maya Vantreight | A relative, same surname | The surname, then decide |
The Southern District of Alabama’s guidance, written for lawyers filing documents, puts the rule in one line: do the replacement for all instances and for all variants of the text you need to redact. It also cautions against partial replacements that leave enough to recover the original.
Match case and whole words, used deliberately
Two options under More change what a search catches. Match case limits the search to the capitalization you typed, which helps tell a surname from an ordinary word and hurts if it makes you miss VANTREIGHT in a header. Find whole words only stops partial matches; Microsoft’s example is changing One to Two without turning Someone into Sometwo. For a name, leave it off on the first pass so you catch it inside email addresses.
Numbers have a shape, and Word can search for it
A Social Security number has a fixed pattern, and Word can search by pattern. In Advanced Find & Replace, select Use wildcards and search for [0-9]{3}-[0-9]{2}-[0-9]{4}. Microsoft’s table of wildcards documents both pieces: a range in brackets matches one character, and a number in braces sets how many times it repeats. The same idea works for phone numbers and account numbers once you know their format.
Searching by pattern finds numbers you did not know were there, which is the point, and it also finds some that are not identifiers, so this step stays Find Next rather than Replace All. The same idea works for any number with a fixed format, and tax files at a CPA firm are full of them.
Headers, footers, footnotes and text boxes live apart from the body
The body is the part of a Word file everyone reads. The header, the footer, the footnotes and the text boxes are stored as separate pieces, and in our test each one held a detail the body did not: the client’s surname and initial in the header, her cell number in a footnote, a sticky note in a text box telling the team when to call her.
Check each of these by opening it, rather than trusting that a search from the body reached it. Double click the header or footer to edit it, as Microsoft describes, read the footnotes at the foot of each page or in the footnote pane, and click into each text box and shape.
One document, several headers
A header is not necessarily one header. Microsoft explains that options such as Different First Page and Different Odd & Even Pages create separate headers and footers, each linked separately to the same type in the previous section. A long agreement with a cover page and several sections can carry half a dozen, and the one you edit is the one you are looking at.
Scroll to the first page, an even page and the start of each section. An engagement letter on letterhead is the classic case, and if yours now mentions AI, our sample disclosure language is drafted for exactly that document.
Footnotes and text boxes
Footnotes are where drafters put the citation, the source of a fact and, often, the detail too specific for the body. Text boxes and shapes are where people put a note to themselves. Both were invisible to at least two of our three extractors, and both were still in the file. That combination is the worst one: nothing warns you, and anything that does read those parts reads them in full.
Fields, tables and embedded objects
Three more places hold text that does not behave like typed text. None of them is exotic, and each one turns up in ordinary office documents.
A field is a small instruction that Word replaces with a result: a date, a cross reference, a page number, sometimes a name pulled from somewhere else in the file. Microsoft notes that you can press Alt+F9 to switch between field codes and field results. Look at both on your copy. The result is produced by the code, so overtyping the result leaves the code behind it untouched; replace the field with plain text or delete it.
Tables are searched, and still worth reading
Text in a table is ordinary text, so Replace finds it. The risk in a table is different: it lines up data that identifies people without names, a date of birth next to a ZIP code next to an employer. Our guide on what makes data deidentified rather than just masked explains why that combination can point to one person as surely as a name.
Embedded objects bring their whole file
When you insert a file through Insert > Object > Create from File, you are embedding a copy of it. Microsoft says embedded objects become part of the Word file. An embedded spreadsheet is the spreadsheet, including rows that do not appear in the small window on the page, and your search in Word does not look inside it. Open each embedded object, clean it at its source, or delete it and paste in only the numbers the AI actually needs.
| Where it hides | Where to find it in Word | What to do |
|---|---|---|
| Tracked changes | Review > Tracking | Accept All or Reject All |
| Comments | Review > Delete | Delete All Comments in Document |
| Hidden text | File > Options > Display | Show it, then delete it |
| White text | Select all, font color | Set to Automatic on a copy |
| Headers and footers | Double click the header or footer | Check every section and first page |
| Fields | Alt+F9 | Replace or delete the field |
| Embedded objects | Click the object | Clean the source or delete it |
Run the Document Inspector last, and know what it cannot see
Word’s own check is the Document Inspector. On the File tab, select Info, choose Check for Issues and select Inspect Document. Microsoft lists what it finds and removes in a Word file: comments, revision marks from tracked changes, document versions, ink annotations, information in headers, footers and watermarks, text formatted as hidden, and invisible content.
It is a good last net and a poor first tool. Microsoft states two limits outright: the inspector cannot detect text hidden by other methods, such as white text on a white background, and it cannot detect objects covered by other objects. It also warns that it is not always possible to restore the data the inspector removes, which is why it recommends running it on a copy of the original.
What it does not look for at all
Notice what is not on the list: the names in your body text. The inspector finds kinds of content, not your client. It will happily pass a document where every mention of the client is still in the visible paragraphs, because that is exactly what a finished document is supposed to contain. The names are your search, and nothing in Word does that search for you. Which details belong in it starts with what counts as sensitive personal information.
The same inspection also covers document properties such as the author and the company. Those belong to a different conversation about what a file says about the people who made it.
If the next step is Copilot inside Word rather than an upload, what Microsoft says Copilot does with your data is covered separately.
What US courts and regulators already ask of a redacted file
Nothing in American law was written for pasting into chatbots, but courts and regulators have been telling people how to redact files for years, and their advice is the best existing standard for this job.
For federal court papers, Rule 5.2 of the Federal Rules of Civil Procedure trims four identifiers down to a stub, as the table shows. It governs filings, not chatbots, yet it is a fair yardstick for how much of a number a careful memo really needs.
| In a federal filing | What Rule 5.2(a) lets it show |
|---|---|
| Social Security or taxpayer ID number | The last four digits |
| Birth date | The year |
| Name of a minor | The initials |
| Financial account number | The last four digits |
The famous public failures, such as the 2019 Manafort filing whose blacked out passages could be copied and pasted, are PDF stories, told in our guide to redacting a PDF before AI. Where a filing also has to disclose that AI was used, the same care applies twice.
The regulators say the same thing more quietly
The FTC’s guide for businesses, Protecting Personal Information, builds its advice on five principles, and the second is scale down: keep only what you need for your business. A document headed to an AI assistant for a summary rarely needs the SSN, the home address or the name of a witness’s daughter.
Health data has the strictest version. HIPAA’s safe harbor method in 45 CFR 164.514(b) requires removing eighteen kinds of identifier, and it covers identifiers of relatives, employers and household members, not just the patient. The daughter hidden in our test memo is that case exactly. What that standard costs a practice is laid out in our HIPAA guide for AI tools.
What Nonimo returns when you give it a Word file
The Nonimo app is installed on your own Mac or Windows PC, and a document dropped into its window never leaves that machine. It hands back a pasteable version of the text, with the details it recognizes swapped for placeholders, plus a covered copy of the file itself. For a .docx, that copy is still a Word file, and its title and properties are covered as well. Nothing is deleted: the placeholders are pseudonyms, and the real values reappear on your screen once the AI’s reply is back in the app. The tool at the top of this page is the other route: it gives you back the same Word document with the details masked.
Here are the opening lines of our test memo, and what Nonimo returned for them:
Typed
Re: Vantreight v. Castellan Freight Inc.
Our client, Dolores Vantreight, was terminated on March 3, 2026.
What Nonimo returned
Re: [PERSON_1] v. [COMPANY_1].
Our client, [PERSON_2], was terminated on March 3, 2026.The names and the company became placeholders, and the real values come back on your screen with the AI’s reply. Our security page says what the app stores locally, and the license page lifts the monthly word limit.
Inside a .docx, comments, tracked changes, headers, footers, footnotes and text boxes get placeholders just as the body does. Driver’s license photos have their own tool.
Sources
- Microsoft Support, Find and replace text. Home > Editing > Replace; More > Match case; the advice to review hits one at a time; Advanced Find & Replace, Use wildcards and the wildcard table. support.microsoft.com
- Microsoft Support, Replace text (Word training). Find whole words only, with the One, Two and Someone example. support.microsoft.com
- Microsoft Support, Accept or reject tracked changes in Word. No Markup only temporarily hides changes; to remove them you must accept or reject them; Review > Tracking > Accept All Changes. support.microsoft.com
- Microsoft Support, Insert, delete, or change a comment. The arrow by Delete, then Delete All Comments in Document. support.microsoft.com
- Microsoft Support, Word Options (Display). The Hidden text option shows a dotted line under text formatted as hidden. support.microsoft.com
- Microsoft Support, Remove hidden data and personal information by inspecting documents. File > Info > Check for Issues > Inspect Document; what it finds in Word; it cannot detect white text or covered objects; run it on a copy. support.microsoft.com
- Microsoft Support, Track changes in Word. Simple Markup shows tracked changes with a red line in the margin; All Markup shows them on the page. support.microsoft.com
- Microsoft Support, Edit your existing headers and footers in Word. Double click the header or footer you want to edit. support.microsoft.com
- Microsoft Support, Link to previous. Different First Page and Different Odd & Even Pages create separate headers and footers per section. support.microsoft.com
- Microsoft Support, Insert, edit, and view fields in Word. Alt+F9 switches between field codes and field results. support.microsoft.com
- Microsoft Support, Linked objects and embedded objects. Embedded objects become part of the Word file. support.microsoft.com
- Microsoft Support, Embed or link to a file in Word. Insert > Object > Create from File. support.microsoft.com
- US District Court, Southern District of Alabama, Best Practices: Redaction of Information. White font makes words look gone and they are not; replace all instances and all variants. alsd.uscourts.gov
- Federal Rules of Civil Procedure, Rule 5.2. Filings keep only the last four digits of an SSN, TIN or account number, the birth year and a minor’s initials. law.cornell.edu
- BuzzFeed News, January 8, 2019. The Manafort filing, mentioned in one line: copied and pasted, the redacted text showed up in full. buzzfeednews.com
- FTC, Protecting Personal Information: A Guide for Business. The five principles, including scale down: keep only what you need. ftc.gov
- 45 CFR 164.514(b), HIPAA deidentification. The safe harbor list covers identifiers of relatives, employers and household members, plus the actual knowledge test. ecfr.gov
- Claude Help Center, supported file types. DOCX is among the document types Claude accepts. support.claude.com
- Nonimo test memo, September 28, 2026. An invented .docx built by hand, read with python-docx 1.2.0, macOS textutil and LibreOffice, and run through Nonimo.
Nonimo is the software that does this on your own computer: it masks client names and IDs before your text reaches ChatGPT. No account needed, and the app does it without your files leaving your machine.
Common questions
How do you redact in Word?
Work on a copy, then replace each name and number with a placeholder using Home > Editing > Replace, one mention at a time. Accept or reject every tracked change, delete all comments, remove hidden text and check headers, footers, footnotes and text boxes by hand. Finish with File > Info > Check for Issues > Inspect Document. The order matters more than any single tool.
Does black highlighting hide text in a Word document?
Only on screen. Highlighting and font color are formatting, and the characters underneath stay in the file. In our test document, a Social Security number set in black on a black highlight came out in plain text from all three extractors we tried. The Southern District of Alabama warns about the white text version of the same mistake: the words look gone, and they are not.
Does Replace All catch every mention of a name?
It catches the exact string you typed, and people are rarely written the same way twice. In our test memo, a search for the client's full name matched 2 of the 9 places that named her or her family. Search the surname, the first name, initials and the email handle separately, and step through the hits one by one so nothing changes unseen.
Can a tracked deletion undo a redaction in Word?
It can, if the change is left unsettled. A name or address deleted with Track Changes on is still stored as deleted text, and Microsoft's support page says the No Markup view only temporarily hides changes. One of the three extractors in our test returned a deleted street address word for word, even though Word would not show it in the final view. Accept or reject every change before you redact.
Why delete comments before redacting a Word file?
Because a comment can name the client in full when the body does not. In our test memo, a comment held the client's full name and the reviewer's, stored in its own part of the file, and none of the three text extractors we tested would have shown it to you. On the Review tab, open the arrow next to Delete and choose Delete All Comments in Document, then redact.
How do I find hidden text in a Word document?
Turn on File > Options > Display > Hidden text, which shows a dotted line under anything formatted as hidden. You can also search for it with Advanced Find & Replace, using Format > Font and the Hidden effect. Hidden text was the one item all three extractors in our test returned, so it is worth two minutes before any upload.
Can I upload a Word document to ChatGPT or Claude after redacting it?
You can, and whether it is wise depends on the account and its terms as much as on the edit. Claude's help center lists DOCX among the file types it accepts. Check the whole file first, not the page view, because a tool that reads the file may read parts Word is not showing you. The Nonimo app gives you the text with names covered and a covered copy of the .docx.
What does the Document Inspector miss?
Microsoft says it cannot detect text hidden by other methods, such as white text on a white background, or objects covered by other objects. What it removes cannot always be restored, so Microsoft recommends running it on a copy. It is a final check that catches comments, revision marks, hidden text and headers, not a replacement for reading the document.
Can Nonimo cover the names in a .docx for me?
The Nonimo app replaces the identifiers it recognizes with placeholders and returns a version of the text you can paste, along with a covered copy of the .docx, title and properties included. It pseudonymizes rather than deletes, so the real values go back into the AI's reply, on your computer.