CSV Data Masking & Anonymizer

How CSV data masking works

This tool parses a CSV file into rows and columns, then applies regex-based masking rules to the columns you choose. Paste CSV text or drop a file, and each column header is scanned to guess a sensible mask type automatically — column names containing “email” default to email masking, “phone” or “mobile” default to phone masking, and “card” or “credit” default to card masking. You can override any column’s mask type from the dropdown.

Email masking keeps the first character of the local part and the full domain, replacing the rest with asterisks (e.g. j***@example.com). Phone masking keeps the last two digits and masks the rest. Card number masking keeps the last four digits, matching the common “last 4” display convention used by payment processors. Generic masking hides everything except the last four characters of a field, useful for IDs, tokens, or any other sensitive value.

All parsing and masking happens locally in your browser using JavaScript regular expressions — your CSV data is never uploaded to any server, which makes this safe to use on real customer data, test fixtures, or exports that contain personally identifiable information (PII) before sharing them with a team, committing them to a repo, or using them in a demo.