Sheet Diff

Try the live demo

Compare two Excel or CSV files and see what changed, right in your browser.

Sheet Diff matches records using a shared unique identifier, such as a SKU, code or email. Rows and columns can move between versions without losing the connection between records.

Features

• Compare .xlsx and UTF-8 .csv files, including worksheet selection for Excel files.
• Find changed, added, removed and unchanged records, plus added or removed columns.
• Review original and updated values together, filter by status and search records.
• Export the full comparison to Excel, independently of the current filter.
• Explore a built-in inventory example and a draggable before-and-after preview.
• Process spreadsheet data locally in the browser, with bundled scripts and fonts.

Try it locally

No build step or backend is required. With Python 3 installed:

git clone https://github.com/VitorRodi/sheet-diff.git
cd sheet-diff
python -m http.server 4180 --bind 127.0.0.1 --directory dist

Open localhost:4180 and click Try the inventory example, or select your own files. Any static HTTP server can serve dist/.

Development and tests

Node.js 22 or newer is recommended for the development tools.

npm ci
npm test

Generate sample Excel and CSV files, plus an invalid-key CSV fixture:

node fixtures.mjs

The files are written to examples/. Try original.csv and updated.csv directly, or compare original.xlsx with updated.xlsx. Select SKU. Both pairs produce one changed, one unchanged, one removed and one added record, despite reordered columns and rows.

Export the Excel comparison, then optionally verify that report:

node verify-export.mjs /path/to/sheet-diff-comparison.xlsx

The static ExcelJS bundle is committed so the app runs without downloading a library at runtime. After an intentional dependency update, copy node_modules/exceljs/dist/exceljs.min.js to dist/vendor/exceljs.min.js and retain its license.

My role

Personal project developed and maintained by Vitor Rodi. My work covers the browser interface, record comparison logic, CSV handling, Excel report generation, tests, and documentation.

Engineering decisions

• Match records by identity, not position. A shared unique key keeps comparisons meaningful when rows or columns move. Blank and duplicate identifiers are rejected.
• Keep spreadsheet processing in the browser. Comparison and report generation do not require a spreadsheet-upload service.
• Make comparison rules explicit. Values use exact string comparisons; formatting and formulas themselves are outside the comparison scope.
• Verify behavior and exports. Automated tests cover comparison and CSV parsing; the export verification script checks generated Excel reports.

Comparison rules and limits

The first row contains column headers. Choose a shared column with a nonempty, unique value for each record. Duplicate or blank identifiers stop comparison rather than silently dropping records.

Identifier whitespace is trimmed. Other values are compared as exact strings, including case and whitespace. Dates use ISO strings. Formulas require saved calculation results. Formatting, comments, macros and formulas themselves are not compared.

Limits: 5 MB per file, 10,000 data rows and 100 columns per worksheet. CSV supports comma, semicolon and tab delimiters, quoted fields, escaped quotes, multiline values and a UTF-8 BOM. Legacy .xls files are not supported.

Structure

dist/                 Static application, ready to serve
  core.mjs            CSV parsing and record comparison
  app.mjs             File loading, results, search and Excel export
  design.mjs          Interactive preview and demo controls
  export.mjs          Tested Excel report generation
  vendor/             ExcelJS and local Inter fonts, with licenses
tests/                Node.js comparison and CSV tests
examples/             Generated sample files
docs/                 Product screenshots

Privacy

Spreadsheet contents are read, compared and exported in your browser. The app has no spreadsheet-upload endpoint or analytics integration. A host serving the static site may keep normal access logs; those requests do not contain spreadsheet contents.

Contributing

Issues and pull requests are welcome. See CONTRIBUTING.md. Please use synthetic data in examples and bug reports.

License and author

MIT license. See LICENSE and THIRD_PARTY_NOTICES.md.

Built by Vitor Rodi.