Compare Two CSV Files Online

To compare two CSV files online, upload both files to Large CSV Viewer's compare tool and select a key column to match rows. Added rows are highlighted green, removed rows red, and changed cells yellow. The diff result is downloadable as a CSV. Free, no account required, works on files of any size.

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Compare two CSV files online for free and see exactly what changed. Highlight added, removed, and modified rows instantly. No install needed.

Need to find what changed between two versions of a dataset? Large CSV Viewer's CSV diff tool compares two CSV files row by row, highlights additions, deletions, and modifications, and lets you download a complete diff report — no coding required.

Key features

  • Added rows highlighted green, removed rows red, changes yellow
  • Match rows by any key column (ID, email, etc.)
  • Works on files of any size — comparison runs server-side
  • Download the diff result as a CSV report

How it works

  1. Upload both CSV files. Upload your 'before' CSV and your 'after' CSV. Both files appear side by side for comparison.
  2. Select a key column. Choose the column that uniquely identifies each row (e.g. ID, email address). This is used to match rows between the two files.
  3. Review and download the diff. Added, removed, and changed rows are color-coded. Download the full diff report as a CSV file.

Ready to try it?

Free, instant — no account or install needed.

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Frequently asked questions

What does the CSV compare tool show?

It shows rows that were added (in the second file but not the first), removed (in the first but not the second), and modified (present in both but with changed values).

Do the two CSV files need to have the same columns?

They should have the same or similar column structure. Columns present in one file but not the other will show as empty in the diff output.

Can I compare large CSV files?

Yes. The comparison runs server-side using DuckDB's EXCEPT and INTERSECT queries, so it works on files of any size.

Is the CSV compare tool free?

Yes, completely free. No account, no file size limit, no paywall.

What if my CSV files don't have a unique key column?

You can select any column as the matching key. If no single column is unique, try combining two columns (e.g. first name + last name). A full row-by-row comparison mode is on the roadmap.