CSV Compare

Compare two CSV files by key columns. See added, removed, changed and unchanged rows, the old and new values of each changed field, and column changes. Download a CSV report.

Spreadsheet & Data Tools Runs client-side Free to use

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About the CSV Compare

CSV Compare finds what changed between a baseline file and an updated file. Choose one or more key columns, such as an ID, and the tool matches rows by key, so rows that only moved to a different position are not reported as changes.

It reports rows added, removed, changed and unchanged, and for each changed row the column with its old and new value. Columns added or removed are reported separately. Duplicate or blank keys must be resolved before comparing. Case and whitespace options are explicit, and the full report downloads as CSV.

How to use

Load the baseline (old) CSV and the updated (new) CSV.
Choose the key column(s) that identify a row.
Choose case and whitespace options and see which columns are compared.
Resolve any duplicate or blank keys.
Review the summary and changes, then download the report CSV.

Key features

One or more key columns.
Added, removed, changed and unchanged counts.
Changed fields with old and new values.
Row moves are ignored in key mode.
Duplicate and blank key detection with explicit resolution.
Column additions and removals reported separately; CSV report download.

Best practices

Use a stable ID as the key.
Turn on whitespace trimming for exports from different systems.
Fix duplicate keys at the source when possible.

Benefits

Audit data changes in seconds.
Clear, shareable change reports.
Private: both files stay on your device.

Frequently asked questions

Why are reordered rows not changes?

In key mode rows are matched by their key, not their position. A row is “changed” only if a compared value differs.

What happens with duplicate keys?

Comparison is blocked and the duplicates are listed. You can fix the files, add another key column, or choose to match duplicates by order of appearance.

What does the report contain?

One line per changed field (change type, key, column, old value, new value), plus one line per added or removed row and per added or removed column.

Is my data uploaded?

No. Files and pasted data are processed only in your browser. Nothing is uploaded or stored, and the tool keeps working offline once the page has loaded.