mask

Masks sensitive fields for anonymization. Supports redaction, deterministic hashing (preserves joins), and type-compatible randomization.

# Redact email and phone fields
undatum mask data.csv --fields email,phone --method redact --output masked.csv

# Hash user IDs (deterministic, preserves joins)
undatum mask data.jsonl --fields user_id --method hash --salt my-salt --output masked.jsonl

# Randomize age and email fields
undatum mask data.csv --fields age,email --method randomize --output masked.csv

Masking methods:

• redact (default) - replace values with a fixed token (***)
• hash - deterministic one-way hash; the same input always produces the same output, so joins across files are preserved. Use --salt for additional security
• randomize - replace values with random but type-compatible values

Reference

Reads: any readable format · Writes: any writable format; CSV/TSV/JSON/JSON Lines on stdout · Memory: streaming · Engines: python

undatum mask [OPTIONS] INPUT_FILE

Argument	Description
INPUT_FILE	Path to input file. (required)

Option	Description	Default
-o, --output TEXT	Optional output file path. If not specified, prints to stdout.
-f, --fields TEXT	Comma-separated list of fields to mask (e.g., 'email,phone,ssn').
--method TEXT	Masking method: 'redact' (default), 'hash', or 'randomize'.	redact
--salt TEXT	Optional salt for hash method (for additional security).
-d, --delimiter TEXT	CSV delimiter character (auto-detected when omitted).
--quotechar TEXT	CSV quote character (iterabledata default '"' when omitted).
--encoding TEXT	File encoding (e.g., 'utf8', 'latin1').
--verbose / --no-verbose	Enable verbose logging output.	--no-verbose
-F, --format-in TEXT	Override input file format detection (e.g., 'csv', 'jsonl').
-O, --format-out TEXT	Override output file format (e.g., 'csv', 'jsonl').
--table, --sheet TEXT	Table or sheet name for multi-table sources (Excel, SQLite, lakehouse).
--start-page INTEGER	Sheet index (0-based) for Excel files.	0
--trust	Acknowledge pickle deserialization risk when reading pickle sources.
--on-error TEXT	Parse-error policy: raise (default), skip, or warn.
--error-log TEXT	Append parse errors as JSONL (use with --on-error skip or warn).
--flatten-nested	Unfold nested dict / array-of-dict fields into dotted paths (e.g. city.lat).
--max-nested-depth INTEGER	With --flatten-nested, maximum nest depth to unfold (engine default 5).
--keep-nested-parents / --no-keep-nested-parents	With --flatten-nested, keep parent dict/array fields alongside dotted children.	--keep-nested-parents

See also shared options.