CSV Validator
Check that a CSV is well-formed before importing it, and get a list of problems with line numbers.
Processed locally in your browser· Your data stays in your browser.
What is CSV Validator?
A CSV that opens fine in a spreadsheet can still break a strict importer: one row with an extra comma, a quote that is never closed, or two columns with the same header name. Finding the culprit in thousands of lines by eye is slow.
This validator parses the file, then checks that every row has the same number of columns as the first row, that quoted fields are properly closed and escaped, and that header names are unique and not empty. Line numbers refer to the source text, even when a quoted cell spans several lines.
How does it work?
- Paste the CSV or open a file; the delimiter is detected automatically unless you choose it.
- Untick "First row is a header" if the first line is data, which disables the header checks.
- Read the status banner and the problem table: each entry gives the line, the type and an explanation.
- Fix the lines in your source file, paste again and confirm the status turns green.
Common use cases
- Verifying an export before uploading it to a strict import tool or database loader.
- Locating the row that breaks a CSV parser in a data pipeline.
- Detecting an unclosed quote that swallows the rest of a file into one cell.
- Checking that hand-edited data still has consistent columns.
Examples
Try this input in the tool above:
id,name,name, 1,Alice,Martin,x 2,Bob 3,"Chloé,Nice,extra,cells 4,David,Roux,y
Line 1: [Header] Duplicate header name "name" (columns 2 and 3). Line 1: [Header] Column 4 has an empty header name. Line 3: [Column count] Row has 2 column(s), expected 4. Line 4: [Quotes] A quoted field opened here is never closed, so the rest of the file is read as a single cell. Line 4: [Column count] Row has 2 column(s), expected 4.
Privacy
CSV Validator runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.
Limitations
The validator checks structure, not meaning: it cannot know whether a date or an email is correct. Only the first 5,000 problems are listed.
Frequently asked questions
What counts as an error and what as a warning?
Wrong column counts and quoting problems are errors because they break parsers. Duplicate or empty header names are warnings: the file is readable but the columns are ambiguous.
Why do line numbers skip when a cell contains a line break?
A quoted cell can span several physical lines. The reported number is the line where the row starts in your text, which matches what you see in an editor.
Does an empty line count as a row?
No. Blank lines are ignored by the validator and by most CSV parsers.
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