Anonymize an Excel or CSV file before an AI analyses it
Drop an .xlsx, .xls or .csv file. Every text cell that names someone, such as a client, an employee, an email, a phone or account number, becomes a code; amounts and dates stay readable, so the AI can still sum, sort and chart. Download the coded copy, give it to the AI, and restore its output 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.
Why spreadsheets leak more than they show
A spreadsheet sent to an AI carries more than its visible cells: hidden columns and sheets, cell comments, links such as mailto: addresses inside formulas, and the author in the file properties. The coded copy is rebuilt from the values: formulas, links and comments are removed, and sheet names are coded like the cells.
- Coded: names, companies, emails, phone numbers, IBANs, ID numbers, addresses, and long numbers stored as numbers, such as a phone number typed as 447700900461.
- Readable: amounts, quantities, dates, column headers and ordinary words such as a product line or a region.
The free tool takes up to 1,000 rows at a time. A ledger, a payroll file or a CRM export with thousands of rows is what the Hidden Tokens app is for: it detects column types from the headers, codes the whole workbook with one key, and puts the real names back into the AI's Excel file.
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 ChatGPT still compute totals on a coded spreadsheet?
Yes. Amounts stay as numbers and the same client always has the same code, so totals by client, top 10 lists and pivot tables work. Restore the AI's table here afterwards.
What about a CSV export from a CRM?
Drop the .csv file: the coded copy comes back as a CSV with the same columns. For exports over 1,000 rows, use the Hidden Tokens app.
Are the formulas kept?
No. The coded copy keeps each cell's value but removes formulas, because a formula can contain an email address or a link. Keep your original for the formulas.
Can I restore an Excel file produced by the AI?
Yes. In the Restore tab, drop the .xlsx or .csv the AI produced, in the same browser tab: the codes in every text cell and sheet name become the real values again.
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.