CSV anonymizer
Replace selected identifiers with consistent keyed pseudonyms across UTF-8 CSV files. Pseudonymization does not make data anonymous.
Accepted files: .csv,.tsv,text/csv,text/tab-separated-values. Multiple files supported. Up to 1 MB in total.
Choose 1 to 10 strictly decoded UTF-8 CSV files. Selected exact headers must exist in every file. Maximum 1,000,000 aggregate file bytes, 10,000 aggregate data records, 100 columns per file and 100,000 aggregate data cells. Mapping export is bounded to 10,000 distinct original values. Aggregate CSV output is capped at 4,000,000 characters. The secret remains in browser memory during use; secure memory erasure is not claimed. Selected columns are pseudonymized consistently across files. Review remaining data for identifiers. Up to 1,000,000 characters. Review the settings before running.
Your result
How to use CSV anonymizer
- Choose one or more UTF-8 CSV files and list the identifying column headers.
- Enter a private random secret of 32 to 1,024 UTF-8 bytes and keep it separately.
- Review and download all pseudonymized files. Export the sensitive original-to-token mapping only when explicitly needed.
Useful next steps
Pseudonyms remain linkable
The same secret and exact value produce the same full-length HMAC-SHA256 token across files and selected columns. Matching is case-sensitive and preserves spaces. Empty selected cells remain empty. Repeated tokens reveal repeated identifiers, and a weak or exposed secret permits guessing attacks.
Review the whole dataset
Unselected values, headers, filenames and combinations of attributes can identify people. This tool does not guarantee anonymity, irreversible de-identification or legal compliance. Normal reports exclude the secret and selected cell values. Mapping export is unchecked by default and contains sensitive original identifiers when enabled.
Local processing and exact strings
Processing runs on your device. CSV downloads quote every cell and protect spreadsheet formula prefixes by default, which changes affected strings. Preserve original cells is for trusted machine processing. Import identifiers as text in spreadsheet applications to preserve leading zeros.