CSV Preflight — free CSV structure & key checks

Review a CSV before an import. CSV Preflight checks uneven records, blank or repeated headers, blank/missing keys, repeated exact keys and possible spreadsheet formula markers. Run it in your browser or download the HTML and use it offline. Open a local UTF-8 CSV or paste text; the tool does not upload, save or rewrite your data.

Supports comma, semicolon and tab; quoted multiline fields, escaped quotes, Unicode and leading-zero IDs. An optional key must be one exact, unambiguous column name. Limits: 5 MiB, 50,000 data records and 200 fields per record. Download a JSON summary without raw cell values. Try the included synthetic sample.

Structural checks only: no cleanup, formula evaluation, fuzzy matching or two-file comparison. Negative numbers or intentional formulas may trigger warnings. A clean report does not guarantee a correct or safe import. No analytics or external dependencies. The ZIP includes the standalone HTML, README, license and verification note.

Free and fully functional on its own. If you need exact comparison of two exports with HTML/JSON and a cell-change log, CSV Diff Desk 1.0.0 is a separate US$29 Python download: https://ko-fi.com/s/a501f4a41d . Python 3.10+ required; paid package tested on Windows with Python 3.12. No purchase is required for CSV Preflight.

AI disclosure: created with Codex by Miga Studio. Code and text were generated with AI and checked locally. Ten functional checks passed; browser sample and JSON download verified, with desktop and narrow layout checks. Other browsers, operating systems and screen readers have not all been tested.

Support: miga-ai-studio-20261010@agentmail.to. Please send synthetic reproductions rather than private records or credentials.