Anonymize a contract before an AI reviews it
Paste a clause or drop the Word file. Parties, signatories, addresses, company and bank numbers become codes such as COMPANY-001; amounts, dates and the legal wording stay readable, because that is what the AI has to review. Then restore its comments here, with the real names, in this tab only.
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 an AI needs to review a contract, and what it does not
Contract review is where AI saves the most time, and where the most sensitive names travel: the client, the counterparty, the guarantor, the people who sign. The AI needs none of them to spot a one-sided limitation of liability or a missing termination right.
- Code: the names of the parties and their representatives, registered addresses, company and VAT numbers, bank details, property or land references, and any project code name that would reveal the deal.
- Keep readable: the clauses themselves, defined terms such as the Supplier, amounts, percentages, notice periods and dates. Change them and the review is worthless.
- Check the clues: a contract can identify a party without naming it (“the only licensed operator of the port of …”). Add such phrases under Adjust → Also code.
- Drop the .docx in the Word or Excel tab, or paste the clauses you want reviewed.
- Ask the AI your question on the coded version: “List the clauses unfavourable to
COMPANY-002and propose redlines.” - Paste its answer in Restore, or drop the Word file it produced: the parties come back, formatting kept.
For a data room or a whole matter, the Hidden Tokens app codes every document with one key, so COMPANY-002 is the same counterparty in the share purchase agreement, the disclosure letter and the board minutes.
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
Will the AI still understand who is who?
Yes. Each party keeps one code throughout the contract, and defined terms such as the Buyer or the Licensor stay readable. The AI follows the obligations of each party without knowing their names.
Are amounts and dates coded?
No. Prices, caps, percentages and dates stay readable because the review depends on them. A figure alone does not identify a party; if one does in your case, add it under Adjust.
Does the Word formatting survive?
Yes. The coded copy keeps headings, numbering and tables, and the file the AI gives back is restored with the same layout, under a generic file name.
Is this enough for professional secrecy?
It removes the direct identifiers from what the AI receives. Indirect clues can remain, so read the coded version before sending it. For law firms, our page on AI and client confidentiality explains the rest of the method.
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.