Compare CSV and JSON online: find added, removed and changed records

Compare two datasets to find added, removed and changed records and download a report.

Local comparison: datasets stay in your browser

Previous version

Current version

Unique key (optional)

Need to fix or normalize the datasets first?Open Data Transformer

Compare CSV or JSON locally using a unique key or row position. The report separates added, removed, unchanged records and modified fields, and can be downloaded as a shareable HTML file.

How to use this tool

Choose CSV or JSON and paste the previous and updated versions into the two panels.
Enter a unique key column, such as id. Leave it empty only if you want to compare rows by position.
Click Compare, inspect the record counts and changed fields, then download the HTML report.

Example input and result

Select CSV and use id as the key. Record 1 changes city, record 2 is removed and record 3 is added.

Input

Before:
id,city
1,Rome
2,Milan

After:
id,city
1,Turin
3,Naples

Result

Added: 1 (id 3)
Removed: 1 (id 2)
Changed: 1 (id 1, city: Rome → Turin)
Unchanged: 0

Supported formats

Compare two CSV datasets with headers or two JSON datasets consisting of an object or an array of objects. CSV supports comma, semicolon and tab delimiters.

Columns from both datasets are compared together. The HTML report includes a summary and details of added, removed and changed records.

Limits and useful checks

The key must exist in both datasets and be non-empty and unique. The tool reports duplicate or missing keys instead of arbitrarily choosing a record.
Without a key, each row is compared with the row at the same position: reordering rows can therefore appear as changes.
Values are compared as text: whitespace and capitalization can produce differences. Downloaded reports contain record data; review their contents before sharing.

Frequently asked questions

Can I compare exports with rows in a different order?

Yes. Use a stable key, such as a record ID, to compare the same items regardless of their position.

Does the tool modify the original datasets?

No. It analyzes both inputs in your browser and generates a difference report. Use Data Transformer to edit the data.

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Limits and useful checks

The key must exist in both datasets and be non-empty and unique. The tool reports duplicate or missing keys instead of arbitrarily choosing a record.

Without a key, each row is compared with the row at the same position: reordering rows can therefore appear as changes.

Values are compared as text: whitespace and capitalization can produce differences. Downloaded reports contain record data; review their contents before sharing.