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CSV Join Workbench

Join two CSV tables by explicit composite keys with inner, left or full record-preserving joins.

✓ Browser-local processing

Result

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How to use CSV Join Workbench

Construct related records rather than compare physical lines. Matching uses exact cell text, and duplicate-key expansion requires an explicit many-match policy.

Enter left csv, right csv, left key columns, right key columns.
Choose the settings for csv join workbench, then run the tool.
Review the result and any limitations before copying or downloading it.

Good to know

Up to100,000 input characters,5000 records and100 columns per table. Downloads quote cells, protect formula-like values and disambiguate colliding exported headers.
Blank key cells match other blank key cells exactly. There is no numeric coercion, trimming or database connection. Both source key columns remain in the output.
Processing is local. Output is limited to 1,000,000 text characters unless a stricter file limit is stated.

Common questions

Can duplicate keys multiply rows?

Yes, only when allow-many is chosen. The complete match count is checked before constructing records; an oversized join is refused.

Is this input sent to a server?

No. The application processes this input inside your browser tab and does not save it to persistent storage.

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