Join CSV files online free

Join two CSV files on matching key columns, choose inner, left, or full results, and control duplicate lookup keys without uploading your data.

Join exactly 2 CSV files on a key column you choose in each file, entirely in your browser without uploading either file. Choose an inner, left, or full join; when the right file contains the same key more than once, you can use its first row, last row, or every matching row. The downloaded CSV contains the left columns plus the right-side columns, with suffixes added when column names collide, and includes unmatched rows according to the join type. Each file can be up to 10 MB, with 20 MB allowed across both files. This cap is intentionally lower than the limits on our other CSV tools because the browser must keep the decoded right-hand rows and their lookup structure in memory while it streams the left file and writes the result. If your files differ in size, putting the smaller lookup table on the right reduces that memory pressure.