How to use the masking tool
- Paste text into the box on the left, or drop an HWP, DOCX, XLSX, CSV, PDF or TXT file onto the drop zone.
- The Masked result on the right shows the text with personal data hidden, and tells you how many items of each type were found.
- Uncheck any type you do not want to mask, and the result updates immediately.
- Click Download .txt or Copy to share the result safely by email, chat or on a message board.
What it detects
| Type | Example | Masked result |
|---|---|---|
| Resident or alien registration number | 900101-1234567 | 900101-1****** |
| Mobile or landline phone number | 010-1234-5678 | 010-****-5678 |
| Email address | honggildong@example.com | ho***@example.com |
| Card number (16 digits) | 1234-5678-9012-3456 | 1234---3456 |
- Numbers separated by hyphens, spaces or dots are found, as well as numbers written without separators.
- For registration numbers, the six-digit date of birth and the gender digit are kept and the last six digits are hidden, so the context remains while the person cannot be identified. This is the format commonly used in published Korean government documents.
- Long numbers (registration and card numbers) are processed before phone numbers, so parts of them are not mistaken for phone numbers.
When to use it
- Sharing customer service records: before forwarding consultation notes to colleagues or partners
- Before using AI tools: remove personal data before pasting business documents into chatbots or translators
- Posting screenshots: check quotes and application forms as text before posting them
- Cleaning up spreadsheets: before handing survey response CSV files to an outside analyst
Limits and cautions
Automatic detection is based on fixed patterns, so it is not 100% complete. The following are not masked automatically, so check them yourself before sharing:
- Names, addresses, bank account numbers, vehicle numbers and passport numbers, which come in many formats
- Numbers written out in words
- Text inside images such as scans and screenshots
The tool does not modify your original file; it produces text output only. If you need to keep the formatting of the original HWP or DOCX, use the find-and-replace feature of that program as well. Everything runs in your browser, so the original text is never sent anywhere before it is masked.
Frequently asked questions
Is the original text sent to a server before masking?
No. The text and files you enter are processed only in your browser and are never sent or stored anywhere.
Are names and addresses masked?
Names and addresses come in too many formats to detect automatically. Check and remove them yourself before sharing.
Are alien registration numbers detected?
Yes. They use the same 13-digit format as resident registration numbers (with 5 to 8 as the first digit of the second part), so they are detected too.
Can I keep the original file's formatting?
The tool produces text output. To keep formatting, use the find-and-replace feature of the original program as well.