How to redact a document before uploading it to ChatGPT
AI chats are great at explaining contracts, payslips and medical reports, but whatever you upload leaves your hands for good. Here's how to remove the personal details first and still get a useful answer.
Open the redaction tool Free, no account. The file stays on your device.Quick steps
- Open maskyourdocs and choose the document.
- Mark names, ID numbers and contact details, using Find text and Mask all for anything that repeats.
- Press Export, then Generate, then Download.
- Upload the redacted copy, not the original.
Why redact first
When you upload a file to an AI chat, the provider receives all of it. Depending on the service and your settings, conversations can be stored, reviewed or used to improve models, and you can't take a file back once it's sent. Check your AI tool's data settings, and redact anyway: then the sensitive parts never leave your device at all.
A black box in a PDF doesn't hide anything from AI
AI tools read a PDF's text, not just how it looks. If someone drew a black rectangle over a name in a PDF viewer, the name is still in the file, and the AI reads it straight through the box. The same goes for white text and tiny fonts. AI tools also read text in images, so a blurred screenshot may not hide much either. The fix is to remove the text, not cover it.
What to remove and what to keep
Remove
- Names, signatures and photos
- Account, card, ID and policy numbers
- Addresses, phone numbers and emails
- Dates of birth
- Anything else that identifies you or someone else
Keep, so the answer is useful
- Amounts, dates and durations
- Clauses, terms and conditions
- Test results, symptoms and medicines
- Job titles and roles
How to do it for each kind of file
Mark names and numbers with Find text and Mask all, Select text or Draw box, then export. Marked pages are flattened, so the AI sees black bars and nothing under them. See how to redact a PDF.
Word document
Removed text is replaced with a placeholder. When you export, choose [REDACTED_1], [REDACTED_2]: each distinct name gets its own number, so the AI can still tell the people apart. See how to redact a Word document.
Text, CSV, JSON or an email
Save the text as a file first (.txt, .md, .csv or .json): the tool opens files, and text can't be pasted into it directly. Mark what should go, export, then press Copy text and paste the redacted version straight into the chat.
Screenshot or photo
Draw a box over each detail. The boxes are painted into the pixels, so there's nothing for the AI to read underneath. See how to redact a screenshot.
Tip: tell the AI what the placeholders mean
Numbered placeholders work best when you say what they stand for, without naming anyone. For example: "[REDACTED_1] is the tenant and [REDACTED_2] is the landlord. Explain clause 7 to the tenant." You get an answer about your situation, and the AI never learns who's involved.
Questions
Can ChatGPT read text under a black box in a PDF?
Yes, if the box was only drawn on top. The text is still in the file and AI tools read it. Redaction has to remove the text, which maskyourdocs does by flattening every page you mark.
Will the AI give a worse answer if I redact the document?
Usually not. Keep the amounts, dates, terms and results; the AI rarely needs the names and numbers that identify you.
Which placeholder is best for AI?
The numbered one, [REDACTED_1], [REDACTED_2]. It keeps different people and values distinct, so the AI can still follow who did what.
Can I paste text into maskyourdocs?
Not directly. Save the text as a .txt file, open that, and use Copy text after export to paste the redacted version into the chat.