anonymize spreadsheet data
Mask Personal Data — just pick a file and you're done.
Drop your file here
Choose a file
xlsx, csv files · up to 10MB · first sheet only
Your file never leaves your browser — nothing is uploaded anywhere.
See how to verify your file isn't sent anywhereFree to use, no sign-up or install required.
What to do next
Finds identical rows and keeps just one.
Cleans up leading/trailing spaces, repeated spaces, and line breaks in one pass.
Compares two files and finds the rows that only appear in one.
How to use Mask Personal Data
- 1Choose the Excel/CSV file containing the personal data you want to mask, or drop it into the upload area.
- 2Pick what to mask — phone number, name, or email — and choose the column it's in.
- 3Click Mask data, check how many cells were masked in the preview, then download the result.
When to use this
- Great for hiding part of a phone number or name before sending a customer list to an outside vendor or contractor.
- Useful for masking emails or other personal details before sharing survey or sign-up data internally.
- Handy for scrubbing real customer data out of a screenshot or example table used in a presentation.
Frequently asked questions
Can a masked value be undone afterward?
No — masking can't be reversed. Once a value is replaced with *, it can't be recovered without the original data, so keep a separate copy of the original file if you might need it later.
What happens to values that don't match the expected format?
Only values that exactly match the selected format are masked. Anything in a different format is safely left untouched and skipped.
Does my file really never get sent to a server?
Correct — LocalSheet does all its processing inside your own web browser. Your file data never travels over the network to anywhere. It even works with your internet connection turned off.
Is there a limit on file size or number of files?
For browser performance and stability, we support files totaling up to 10MB. Merging files supports up to 20 files at once.
Is there a fee, or do I need to log in?
No. Every LocalSheet tool is completely free, with no account and no login required.