CSV check

Find import problems without losing your data.

Check your CSV before importing

Find mismatched rows, duplicate headers and spreadsheet formula risks. Everything runs in this browser; your file is never uploaded.

Choose a UTF-8 CSV fileOr paste CSV text

Up to 2 MiB, 20,000 records, 250 columns and 250,000 cells. UTF-8 only; other encodings are rejected.

DelimiterFirst record contains column headers

Choose a file or paste text to begin.

Read the CSV example results

Try an example loads comma-separated text and analyzes it with a header. With the export options off, 00042 keeps its leading zeros and the comma inside the quoted note stays in one cell.
Expect 4 data records and 3 header columns. Record 4 (line 4) has only 2 cells; there is also 1 cell with surrounding whitespace and 1 formula candidate, =1+1. These are warnings to review, not automatic repairs or proof that the destination will accept the data.
Turn on trimming and the formula prefix to compare the copy: 1 cell is trimmed and 1 gets an apostrophe before =1+1. Highlighted cells show those changes. Empty-record removal removes nothing in this example; the short record stays short. Review the full-copy change counts before downloading.

For a separate ID and date check, paste id,long_id,date on the first line and 00042,900719925474099312345,2026-10-14 on the second. Choose comma and analyze with all export options off. All three values remain strings with the same spelling in the copy.

Choose the right CSV download

All options are off by default. IDs, leading zeros, dates and long numbers stay strings here. Spreadsheet apps can still auto-convert values when opening a CSV; import columns as text to retain them.

The copy uses the output delimiter shown above, UTF-8 and CRLF record separators. Quoting may change; embedded line breaks and BOM presence are retained. Ragged rows and duplicate headers are never automatically repaired because their intended structure cannot be inferred safely. The original stays untouched.

For a selected file, the original download preserves its exact bytes. Pasted text is downloaded from the browser text value as UTF-8, so earlier encoding or line-ending bytes may not be preserved.

CSV check

Check your CSV before importing

Diagnostic results

What we found

Original values

Export a separate copy

Downloaded-copy values