Remove CSV duplicate records by a unique key

Step-by-step approach

Identify the stable business key such as CustomerID or OrderID.
Investigate why duplicate keys occurred before deleting records.
Run key-based deduplication and choose the exact header.
Compare removed records against source; the first matching row is retained.
Use the exported CSV only after confirming key uniqueness is intended.

Try the matching tool

Open CSV Deduplicate by Key to work on a local copy. Review the result before importing it elsewhere.

What this does not solve

Browser tools can validate known structures and transform available data, but cannot restore deleted or corrupted bytes, infer unknown business facts, or guarantee that a target system will import every field as intended.