CSV Validator — RFC 4180
About CSV Validator
The CSV Validator scans comma-separated data for structural problems before an import reaches a spreadsheet, database or API. It reports broken quote placement, unclosed quoted fields, inconsistent row widths and duplicate header names in one structured report.
Validation targets RFC 4180 behavior, including doubled quotes inside quoted fields and CRLF record separators. Everything runs locally in your browser, so production exports and customer data are never uploaded.
How it works
Strict quote scanning
Quoted fields may contain commas, CRLF line breaks and doubled quote characters. Quotes inside an unquoted field, characters after a closing quote and missing closing quotes are reported with their line and column.
Consistent row widths
The first row establishes the expected column count. Every later row is compared with it, exposing truncated records and accidental extra delimiters.
Headers and line endings
Header mode identifies duplicate column names. The optional line-ending check reports bare LF or CR separators because strict RFC 4180 records use CRLF, while keeping those findings as warnings for practical interoperability.
Frequently asked questions
Does a comma inside a value make the CSV invalid?
Not when the complete field is wrapped in double quotes. A comma in an unquoted field creates another column and can produce an inconsistent-row error.
How are quotes escaped in CSV?
Inside a quoted field, write two consecutive double quotes. A single quote character in the middle of an unquoted field is reported as broken quoting.
Are LF-only files rejected?
They remain parseable, but strict line-ending mode reports each non-CRLF separator as a warning so you can normalize the file when exact RFC 4180 output matters.
Sources & last verified
The behaviour of this tool and the claims on this page were checked against the specifications below on . Everything runs in your browser, so the output you see is exactly what the engine produced.
Found a wrong result or an outdated claim? Report an error and it will be re-verified.