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CSV Validator

100% Free

Validate CSV structure instantly — catch unclosed quotes, inconsistent column counts, empty or duplicate headers and blank rows, with line-numbered errors and warnings.

RFC 4180
Instant Check
100% Client-Side
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<iframe
  src="https://tools.town/embed/csv-validator/"
  width="100%"
  height="600"
  style="border:none; border-radius:12px;"
  loading="lazy"
  title="CSV Validator">
</iframe>

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How to Use

  1. 1 Paste your CSV, upload a .csv file, or load the sample
  2. 2 Pick the delimiter — comma, semicolon, tab, or pipe
  3. 3 Tell the validator whether the first row is a header
  4. 4 Read the status banner: valid, or a count of errors
  5. 5 Fix the issues using the line-numbered error and warning lists

Features

  • RFC 4180 parsing with quoted-field and embedded-newline support
  • Detects unclosed quotes, wrong column counts, and empty rows
  • Flags empty header names and warns on duplicate headers
  • Reports data rows, column count, and total rows at a glance
  • Comma, semicolon, tab, and pipe delimiters
  • Runs entirely in your browser — your data never leaves your device

Why it Matters

A single ragged row or a stray unescaped quote can break an entire CSV import, and the error message a database or spreadsheet gives back is often cryptic. Validating the structure first — with the exact line number of each problem — turns a frustrating trial-and-error import into a quick fix before the data ever reaches your pipeline.

★★★★★

Use Cases

Pre-Import Checks

Catch malformed rows before loading data into a database or app

Data Cleaning

Find the rows with the wrong number of columns in a messy export

Spreadsheet Exports

Confirm a CSV from Excel or Sheets is well-formed before sharing

Learning CSV

Understand quoting, delimiters, and the RFC 4180 rules

What this tool does

The CSV Validator checks whether a CSV file is structurally sound before you try to import it. Paste or upload your data, pick the delimiter, and it reports a clear pass/fail status alongside a count of rows and columns and a line-numbered list of every error and warning it found.

How it works

The validator parses your input with an RFC 4180 tokenizer that understands quoted fields, escaped quotes, and embedded newlines. It then checks each row against the expected column count, inspects header names for emptiness and duplicates, and notes any blank rows. The pure validateCsv function returns a structured report, so results are deterministic.

Privacy

Everything runs locally in your browser. Your CSV is never uploaded, logged, or stored.

Frequently Asked Questions

What counts as an error versus a warning?
Errors are structural problems that would break most parsers — an unclosed quote, a row with the wrong number of columns, or an empty header name. Warnings are things worth knowing but not necessarily fatal, like a fully empty row or a duplicate header name. A file is reported valid only when there are zero errors.
Does it handle commas inside quoted fields?
Yes. The validator follows RFC 4180, so a field wrapped in double quotes can contain commas, line breaks, and escaped quotes (written as two double quotes). Those are parsed as part of the field rather than as new columns or rows.
Which delimiters are supported?
Comma, semicolon, tab, and pipe. Semicolon files are common in locales that use a comma as the decimal separator, and tab-separated values (TSV) are handled by choosing the tab delimiter.
Why does it say a row has the wrong number of columns?
Every row should have the same number of fields as the first row. If a row has more or fewer — usually from a missing value, an extra delimiter, or an unescaped quote — it's flagged with its line number so you can line it up against the header.
Is my CSV uploaded anywhere?
No. Validation happens entirely in your browser. Nothing you paste or upload is sent to a server, logged, or stored.
📖

Want to understand the math?

Browse all guides →
CSV Format Explained
csv

CSV Format Explained: Delimiters, Quoting, and Common Errors

A complete guide to the CSV format and RFC 4180 — how delimiters and quoting work, the most common ways CSV files break, how to read validation errors, and how to validate a file before importing.

23 Jun 2026

5 min read

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