CSV Merger
Merge two CSV files on a shared key column — join related exports into one sheet. Combine two tables without spreadsheets — local merging, free, no signup.
How to Use the CSV Merger
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Frequently Asked Questions
Mismatched columns?
The key column must exist in both tables. Non-key columns from the second table are appended; left rows with no match get blanks.
How many files?
Two tables per run — a left and a right CSV joined on the key. Repeat runs to join more.
Dedupe after merging?
No dedupe step is included — overlapping keys keep the first right-table match. Review the joined output before analysis.
Does merging upload data?
No — merging runs locally in your browser. Data never leaves your device.
Is the merge an inner or left join?
Left join: every left row survives, right-only keys never appear, and unmatched left rows get blank right cells. Headers become left columns plus right non-key columns — the default name-key demo yields name,email,department.
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Last updated October 2026