Utility
CSV Merge Join Tool
Join two CSV files with inner, left, right, or full merges
Paste both CSV datasets to merge them on one or more keys.
Join Two CSV Datasets Quickly
CSV joins are one of the most common data-cleaning tasks. This tool lets you match two pasted datasets by key and preview the merged output without opening a notebook or spreadsheet.
Supported Join Types
Use inner joins to keep only matched rows, left joins to preserve the left dataset, right joins to preserve the right dataset, and full joins to preserve both sides with blanks for unmatched values.
Useful For Analysis And QA
This is helpful for reconciling exports, enriching customer tables, validating ID coverage, and checking which keys fail to match across two sources.
Frequently Asked Questions
What is the difference between inner and left join?
An inner join only keeps rows whose join keys match on both sides. A left join keeps every row from the left CSV and fills unmatched right-side columns with blanks.
Can I join on multiple columns?
Yes. Enter the left and right join keys in the same order, separated by commas. The tool combines those values into one composite match key.
What happens when both CSVs share a column name?
If a right-side column name duplicates a left-side name and it is not the aligned join key, the tool appends _right so the merged output stays unambiguous.
Does this support file uploads?
This version is paste-first. The join runs in the browser on raw CSV text so the source data does not leave your machine.