Validate a CSV column with a regex
Paste CSV, choose a column, and flag values that do not match your required pattern — or invert the check to find forbidden values.
About this tool
Regex Column Validate checks one CSV column against a regular expression and lists which rows fail the rule. Use it for format checks such as ZIP/postal codes, phone-like IDs, invoice numbers, SKU shapes, or any one-column data-quality rule that is easier to express as a regex.
By default the regex must match the whole cell. Turn off full-cell matching when you only need the pattern to appear somewhere inside each value. You can also invert the report to flag values that do match a forbidden pattern.
Worked example
CSV:
name,zip
Ada,12345
Bo,1234
Cy,90210
With column zip, pattern \d{5}, and full-cell matching on, the text report
flags Bo's row because 1234 has only four digits:
Rows checked: 3
Valid: 2
Invalid: 1
row 2 (line 3): "1234" — does not match the pattern
Limits & edge cases
- Regex syntax is Rust
regexsyntax. Backreferences and look-around are not supported by that engine. - Use inline flags such as
(?i),(?m), or(?s)for advanced regex modes. - Numeric column selections are 0-based indexes. Header names work when the header checkbox is on.
max_issuesonly caps the listed rows. The total invalid count is still reported.- Blank cells can be allowed or treated as invalid before regex matching.
FAQ
Does the pattern have to match the whole cell?
By default, yes. The tool anchors the pattern to the full cell so \d{5} means
exactly five digits. Turn off "Require full-cell match" to accept any substring
match inside the cell.
Can I find values that match a forbidden pattern?
Yes. Change "Flag which values" to "Values that match". That inverts the report and is useful for finding all-caps placeholders, test IDs, or other disallowed formats.
How do I use case-insensitive or multiline regex flags?
Use the checkbox for case-insensitive matching, or embed Rust regex inline flags
in the pattern, such as (?i)hello or (?m)^ID-\d+$.
Can it validate multiple columns at once?
No. This focused tool validates one column and one regex rule per run. For a larger schema with multiple rules, use a dedicated data validator or run this tool once per column.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool regex-column-validate "name,zip
Ada,12345
Bo,1234
Cy,90210" 'column=zip' 'pattern=\d{5}'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/regex-column-validate/?data=name%2Czip%0AAda%2C12345%0ABo%2C1234%0ACy%2C90210&column=zip&pattern=%5Cd%7B5%7D&full_match=true&ignore_case=true&report=non-matching&has_header=true&allow_blank=true&delimiter=auto&max_issues=50&output=textMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.