CSV validator for RFC 4180
About CSV Validator
The CSV validator checks comma-separated data for structural problems before you import it into a spreadsheet, database or API. One report lists misplaced quotes, unclosed quoted fields, rows with the wrong number of columns and duplicate header names.
Validation follows RFC 4180, including doubled quotes inside quoted fields and CRLF row separators. It runs in your browser, so exports with customer data are never uploaded.
How it works
Strict quote checks
Quoted fields may contain commas, CRLF line breaks and doubled quotes. The report gives the line and column for a quote inside an unquoted field, text after a closing quote, or a missing closing quote.
Consistent row widths
The first row sets the expected column count. Every later row is compared with it, which exposes cut-off rows and stray delimiters.
Headers and line endings
Header mode flags duplicate column names. The optional line ending check warns about bare LF or CR separators, because strict RFC 4180 uses CRLF. These are warnings, not errors, since most tools accept LF.
Frequently asked questions
Does a comma inside a value make the CSV invalid?
Not if the whole field is wrapped in double quotes. In an unquoted field, a comma starts a new column and can cause a row width error.
How are quotes escaped in CSV?
Inside a quoted field, write two double quotes in a row. A lone quote in the middle of an unquoted field is reported as broken quoting.
Are LF-only files rejected?
No, they still parse. Strict line ending mode reports each non-CRLF separator as a warning, so you can fix the file when exact RFC 4180 output matters.
Sources & last verified
We checked this tool's behavior and the claims on this page against the specifications below on . The tool 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Found a wrong result or an outdated claim?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 we will check it again.
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