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CSV validator: check a file before the import rejects it

Paste a file or open one, describe what each column must contain, and get the list of rows that will not pass, with the reason for each. The file never leaves your browser.

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What it checks

  • Required columns that are missing or empty on a row.
  • Maximum and minimum length, the usual cause of silently truncated text.
  • Types: whole number, decimal number, boolean, email address.
  • Dates in the format the target expects: YYYY-MM-DD, DD/MM/YYYY, MM/DD/YYYY or YYYYMMDD. Impossible dates such as 31/02 are refused.
  • Allowed values, for codes such as incoterms, currencies or statuses.
  • Unknown columns, if you choose to refuse them.
  • File structure: a row with too many values, a duplicated column name, a quote that is never closed.

How to use it

  1. Bring the file. Paste it or open it. Commas, semicolons, tabs and pipes are detected.
  2. Describe the columns. Type them in, or use “Infer the contract from this sample” on a file you know is good, then tighten the limits.
  3. Check. Each problem names the row, the column, the rule and the value received.

Why a file that looks fine still fails

Most import failures are not broken files. They are files that are valid CSV but do not match what the target accepts today: a label that grew past the column size, a date written the other way round, a code the target retired. An import tool often reports this as a generic error on the whole file, or stores a shortened value without a word. Checking the file against an explicit contract before sending it turns that into a list you can fix. The guide on silent truncation covers the most common case.

Once a contract is right, the validation endpoint applies it to every file automatically, and the schema diff shows what a new version of the format would break.

Questions

Is my file uploaded?
No. The file is read and checked by your browser. The site only counts that a check ran, never what was in it.
Which delimiters are supported?
Comma, semicolon, tab and pipe, detected from the header row. Quoted values, doubled quotes and line breaks inside quotes follow RFC 4180.
How large can the file be?
There is no fixed limit in the browser: files of a few thousand rows are checked at once. The first 50 problems are listed, and the total count is always exact.
Can I keep my contract?
It is saved in your browser for next time. “View the contract as JSON” gives a text you can store or share.