Free Online CSV Formatter & Validator
Format, validate, and preview CSV files online. Auto-detects delimiter, checks column consistency, and converts to Markdown tables — 100% client-side.
100% Client-Side · Your data never leaves your browserHow to Use CSV Formatter & Validator
Paste your CSV or TSV content into the Input area, then click Format / Validate or press Ctrl/Cmd+Enter:
- Delimiter — choose Auto to let the tool detect the separator, or pick Comma, Semicolon, Tab, or Pipe manually.
- Trim whitespace — strips leading/trailing spaces from each field value.
- Formatted tab — shows the normalized, RFC 4180-compliant CSV output.
- Markdown tab — converts your data to a Markdown table you can paste into documentation.
- Table Preview — renders the data as an HTML table so you can visually verify column alignment.
The stats bar shows row count, column count, and the detected delimiter. Any rows with mismatched column counts are listed as errors below the output. Press Ctrl/Cmd+K to clear everything.
Frequently Asked Questions
What is RFC 4180 CSV format?
RFC 4180 is the de facto standard for CSV (Comma-Separated Values) files. It defines that fields containing commas, double quotes, or newlines must be enclosed in double quotes. Double quotes inside a quoted field are escaped by doubling them (""). Lines are separated by CRLF. This tool fully supports RFC 4180 when parsing and formatting.
How does the auto-detect delimiter work?
The tool counts unquoted occurrences of comma (,), semicolon (;), tab, and pipe (|) in the first line of your file. The character with the highest count is selected as the delimiter. European CSV exports often use semicolons, while tab-separated values (TSV) are common in database exports. You can override the auto-detected delimiter with the selector in the toolbar.
What do the column count errors mean?
RFC 4180 requires every row to have the same number of fields as the header row. If a data row has more or fewer fields, this tool reports it as an error. Common causes are unquoted commas inside values, missing closing quotes, or trailing delimiters. Fix the offending row in your source and re-format.
Can I convert CSV to a Markdown table?
Yes. After formatting, switch to the "Markdown" tab in the output area to see your CSV rendered as a GitHub-flavored Markdown table. This is useful for pasting data into documentation, README files, or pull request descriptions.
What does "Trim whitespace" do?
When enabled, leading and trailing spaces are stripped from every field value before formatting. This is useful when your CSV was exported with extra padding (e.g., "Alice " instead of "Alice"). It does not affect whitespace inside quoted strings that is clearly intentional.
Is my CSV data sent to a server?
No. All parsing, validation, and formatting happens entirely in your browser. Your data never leaves your machine, making this tool safe to use with sensitive or proprietary datasets.
Does this tool support TSV (tab-separated values)?
Yes. Select "Tab" from the delimiter dropdown (or let auto-detect pick it up) and the tool will parse your TSV file correctly. You can also convert TSV to comma-delimited CSV by choosing a different output delimiter.