CSV Join & Merge
About CSV Join / Merge
CSV Join and Merge combines two tables using matching key columns, providing database-style left, inner and full joins without uploading either file.
How it works
Choose keys independently
Enter one key name when both files use the same header, or leftKey,rightKey when their names differ. Duplicate key values correctly produce multiple joined rows.
Left, inner and full joins
Left keeps every row from A, inner keeps only matches, and full also appends unmatched rows from B.
Collision-safe columns
The right join key is omitted and other duplicate header names receive a right. prefix, preserving all values without ambiguous columns.
Frequently asked questions
What happens when a key occurs more than once?
Every matching pair is emitted, matching relational join behavior.
Which join should I use?
Use left to enrich a primary table, inner to keep matched rows only, and full to retain unmatched rows from both sides.
Are the files uploaded?
No. Both tables are parsed and joined locally.
Sources & last verified
The behaviour of this tool and the claims on this page were checked against the specifications below on . Everything runs in your browser, so the output you see is exactly what the engine produced.
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