Data & CSV

Join two CSV tables

Match rows across two tables using a shared identifier.

Your inputs

Left CSV

UTF-8 CSV/TSV stays on this device. First row contains unique headings; maximum 25 MB, 50,000 rows and 200 columns. Fully empty rows are ignored.

Up to 25 MB per file, 50,000 data rows, 200 columns and 2 million data cells. Fully blank rows and columns are ignored before row, column and cell limits are checked. Individual tools may have smaller result or chart limits.

Or choose a CSV file

Left separator

Right CSV

UTF-8 CSV/TSV stays on this device. First row contains unique headings; maximum 25 MB, 50,000 rows and 200 columns. Fully empty rows are ignored.

Or choose a CSV file

Right separator

Left matching column

Right matching column

Join type

Blank keys

Results update as you type. Larger files run when you press Update result.

Processed on your device

Your result

LOCAL & PRIVATE

Your result will appear here.

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A clear answer. Here’s how.

Matches exact, case-sensitive text keys, preserving leading zeros. Duplicate matching keys produce every matching row combination; output stops at 50,000 rows. Right-hand columns are prefixed Right. with collision-safe suffixes. Left joins retain left order; full joins append unmatched right rows. Empty keys do not match by default; no numeric coercion or trimming is applied.

See a worked example

Worked example

A fixed demonstration, separate from the values you enter above.

Left CSV

ID,Name
001,Ada
002,Sam
003,Jo

Left separator

Comma

Right CSV

ID,Department
001,Design
003,Research
004,Finance

Right separator

Comma

Left matching column

Right matching column

Join type

Left: all left rows

Blank keys

Do not match empty keys

Example result

Example result
ID	Name	Right.ID	Right.Department
001	Ada	001	Design
002	Sam
003	Jo	003	Research

Exact text-key left join. Duplicate keys can expand the result; right columns retain their own key values.