Anonymize a PDF before you give it to ChatGPT
This free tool does not open PDF files. What it does well is code the text inside them: copy the text out of the PDF, paste it below, and names, addresses, company and phone numbers become codes such as NAME-001. Give the coded text to ChatGPT instead of the PDF, then restore its answer here.
Restoring uses the key of this tab: code your text here first, keep this tab open, then come back with the answer.
Adjust
See the key (it stays in this tab)
The key links each code to the real value. It exists only in this tab's memory: close or reload the tab and it is gone.
connect-src 'none' in its security policy) and loads no analytics. Turn Wi-Fi off once the page has loaded: the tool works just the same. The engine is the one inside the Hidden Tokens app.How it works
1 · Code
Paste a text or drop a file. Names, companies, addresses, emails, phone numbers, bank details, ID and case numbers become codes such as NAME-001 or COMPANY-001. Unknown proper nouns are coded too: when in doubt, the engine codes.
2 · Send the codes
Copy the coded text, or download the coded file, and give it to ChatGPT, Claude, Gemini or Copilot. The AI reasons on the codes: it still knows who did what, not who they are.
3 · Restore
Paste the AI's answer in the Restore tab, in the same browser tab. The codes become the real names again, on your screen only.
Example: a letter copied out of a PDF
NOTICE OF RENT ARREARS page 1 of 2
Tenant: Mr Gareth Pendleton
Property: Flat 4, 17 Larkspur Court, Norwich NR2 3HX
Letting agent: Thornfield Lettings Ltd, company no. 07712345
Arrears at 1 October 2026: £2,340.00 (three months' rent
at £780.00)
Mr Pendleton is asked to contact Joanna Reeve on 01603 496012 or at joanna.reeve@thornfield-lettings.example within 14 days.NOTICE OF RENT ARREARS page 1 of 2
Tenant: Mr NAME-001 NAME-002
Property: Flat 4, 17 NAME-003 Court, NAME-004 REF-002 REF-003
Letting agent: COMPANY-001, company no. REF-001
Arrears at 1 October 2026: £2,340.00 (three months' rent
at £780.00)
Mr NAME-002 is asked to contact FIRSTNAME-001 NAME-005 on PHONE-001 or at EMAIL-001 within 14 days.The tenant, the address, the letting agent, its company number and the contact's details are coded; the amounts, dates and page number stay readable. Text copied from a PDF often carries headers and footers: delete what the AI does not need before coding.
Three ways to get a PDF's text to the tool
Uploading the PDF itself to ChatGPT sends everything in it: the text, the names in the signature block, and the file properties. Getting the text out first lets you code it before anything leaves your browser.
- Copy and paste. Open the PDF, select all (Ctrl+A or ⌘A), copy, and paste into the Text tab. Line breaks and page headers come along; that does not stop the coding, but remove what the AI does not need.
- Open it in Word. Word can open a PDF and turn it into an editable document. Save it as .docx and drop it in the Word or Excel tab: you get a coded copy with the layout Word rebuilt.
- Scanned PDF? If you cannot select the text, the PDF is an image. See anonymizing a scanned document: the text has to be recognised first.
What the free tool does not do: read the PDF file itself, or keep the PDF's layout. The Hidden Tokens app reads PDFs and scans on your computer, codes them with the rest of the case file, and never sends the original anywhere.
The free tool or the Hidden Tokens app?
This free tool
- One text or one file at a time
- Up to 3,000 words or 1,000 spreadsheet rows
- The key lives in this tab and disappears when you close it
- Word, Excel, CSV and text
The Hidden Tokens app
- Whole folders: the same person keeps the same code in every document
- One key per case file, kept on your computer
- PDF and scanned documents, read on your computer
- Inside Claude Desktop, and in ChatGPT, Gemini and Copilot with the extension
- Industry packs, firm rules and a signed proof of what the AI saw
A word on the word “anonymize”
Strictly speaking, this tool pseudonymizes: each value is replaced by a code that can be reversed with the key. Under the GDPR, pseudonymised data is still personal data for whoever holds the key, which here is you, in this tab. What the AI receives no longer names anyone directly. Clues can remain, such as a job, a town and an age together: the tool warns you when it sees them. Read the result before sending it.
Questions
Why can't I drop the PDF directly?
A PDF stores text as positioned fragments, not as paragraphs, and reading it reliably needs a heavier engine than this page loads. The free tool takes Word, Excel, CSV and text; the Hidden Tokens app reads PDFs on your computer.
Will ChatGPT still understand the copied text?
Yes. Line breaks in the middle of sentences do not bother it. Each person and company keeps one code, and amounts and dates stay readable.
Does the PDF's metadata matter?
A PDF can carry the author's name, the software and the original file path. When you paste only the text, none of that is sent.
Can I get a coded PDF back?
Not from the free tool. Restore the AI's answer here as text, or ask the AI for a Word document with the codes and restore it in the Restore tab, then export it to PDF yourself.
Other ways to use the free tool
By file type
By AI tool
By task
For whole folders, use the app
Hidden Tokens codes whole case files on your computer with one key, works inside Claude Desktop and in your browser, reads PDFs and scans, and puts the real names back into Word and Excel files.