Check a CSV before it reaches an import pipeline.
Offline CSV Preflight is a small Python command-line checker for structural problems and exact duplicate keys. It reads a file and emits a JSON report; it does not rewrite the input or send it over a network.
What it checks
It detects repeated or whitespace-padded header names, missing configured columns, rows with the wrong number of fields and exact duplicate key values. The fixtures cover malformed rows, quoted commas and newlines, a UTF-8 byte-order mark, empty input and preservation of the original bytes.
How to use it
Configure required columns and the key field, run the checker locally, then review its JSON findings before your own import process. The tool is a preflight report, not a data transformation.
Read source and usage on GitHub
Evidence boundary
This is an independent sample built around synthetic data. It does not decide which duplicate record to keep, cover every CSV dialect or business rule, or certify that a file is safe to import. Review the report and validate requirements for your destination system.