Anonymize a document before you give it to Claude
Drop a Word, Excel, CSV or text file below and download a coded copy to attach in Claude. Names, companies, addresses, emails, phone, bank and ID numbers are replaced by codes; the formatting stays. Claude works on the codes, and you restore its answer here, in this tab.
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.
What Claude receives from an attached file
When you attach a file to Claude, its whole content is sent to Anthropic, including parts you do not see on screen: comments, tracked changes, the author and company in the file properties, hidden spreadsheet columns, cell comments. A coded copy removes or codes all of them.
- Word: the text of the body, headers, footers and notes is coded paragraph by paragraph, formatting kept. Comments and tracked changes stay, coded, so Claude can still read the discussion. Author, metadata, images and hidden fields are removed.
- Excel and CSV: every text cell is coded; amounts stay readable so Claude can compute totals. Formulas, links and cell comments are removed; sheet names are coded too.
Working in Claude Desktop every day? The Hidden Tokens connector codes whole folders from inside Claude, reads PDFs and scans on your computer, and writes the decoded Word file next to your originals.
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
Can Claude still analyse a coded contract?
Yes. Clauses, dates, amounts and the roles of each party stay readable; only who the parties are is replaced by codes. Ask Claude to answer with the codes, then restore its answer here.
Does it work with PDF files?
Not in the free tool. The Hidden Tokens app reads PDFs and scanned documents on your computer and codes them the same way.
Does Anthropic train on my files?
That depends on your plan and settings. Either way, Claude receives what you attach. With a coded copy, it never receives your client's identity.
Why is the downloaded file called document-coded.docx?
A file name can contain a client's name, and file names are sent to the AI too. The generic name is deliberate.
Other ways to use the free tool
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.