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 Compare Two CSV Files

Use this free online CSV comparison tool to quickly find differences between two CSV files. Upload or paste your CSV data, select a comparison mode, and instantly see which rows were added, removed, or modified — including cell-level changes. All processing runs entirely in your browser, so your data stays private.

Processing…
File A Original
 
File B Updated
 
⚙️ Comparison Options
Load CSV data first to select key columns.
🔁 Column mapping Map columns with different names between File A and B.
Rows A
–
Rows B
–
Unchanged
–
Modified
–
Added
–
Removed
–
Changed cells
–

⭐ Compare Two CSV Files – Explanation & Examples

The Compare Two CSV Files tool lets you instantly find differences between two CSV datasets directly in your browser. Whether you are auditing data exports, validating database migrations, reconciling reports, or tracking changes between two versions of a file, this tool gives you a complete, cell-level diff in seconds — with no data ever leaving your device.

⭐ What Does This Tool Do?

The CSV comparison tool identifies:

  • Added rows — records present only in File B
  • Removed rows — records present only in File A
  • Modified rows — rows that exist in both files but contain at least one changed value
  • Unchanged rows — identical records across both files
  • Cell-level differences — exactly which column changed, and what the old and new values are

Results are shown in a colour-coded dashboard with tabs for each diff category. You can filter by keyword or column, and export in CSV or JSON format.

⚙️ How to Use the Tool

  1. Upload a CSV file or paste CSV text into the File A (Original) panel.
  2. Upload or paste your updated data into the File B (Updated) panel.
  3. Choose your comparison mode (Key column, Row by row, or Full file).
  4. If using Key column mode, check the column(s) that uniquely identify each record (e.g. ID or Email).
  5. Set any ignore options (case, whitespace, empty values).
  6. Click Compare to run the diff.
  7. Browse the results tabs, filter by keyword, and export what you need.

🔎 Comparison Modes Explained

Key Column Comparison (recommended)

Match rows using one or more unique identifier columns. For example, if your CSV has an ID column, the tool uses it to find the same record in both files regardless of row position. This is the most reliable mode for real-world data where row order may differ between exports.

Row-by-Row Comparison

Compare records strictly by position — row 1 in File A is compared to row 1 in File B, and so on. Use this mode when your files have the same structure and sort order and you simply want to spot positional changes.

Full File Comparison

Treat each row as a unique signature and identify which rows are unique to each file. This mode ignores order entirely and is ideal for unordered datasets where you want to know the unique records in each file.

⚙️ Ignore Options

  • Ignore case — treats ALICE and alice as equal.
  • Ignore whitespace — trims leading/trailing spaces and collapses multiple spaces.
  • Ignore row order — rows do not have to appear in the same sequence.
  • Ignore column order — column positions do not need to match.
  • Treat empty as null — blank cells and missing values are treated identically.

🔎 Example: Key Column Comparison

File A (original):

ID,Name,Email,Revenue
1,Alice,alice@example.com,1500
2,Bob,bob@example.com,2200
3,Carol,carol@example.com,800
4,Dave,dave@example.com,3100

File B (updated):

ID,Name,Email,Revenue
1,Alice,alice@example.com,1500
2,Bob,bob@newemail.com,2450
5,Eve,eve@example.com,950

Results using key column ID:

  • Added — Row with ID 5 (Eve)
  • Removed — Rows with ID 3 (Carol) and ID 4 (Dave)
  • Modified — Row with ID 2 (Bob): Email and Revenue changed
  • Unchanged — Row with ID 1 (Alice)

⚙️ Column Mapping

If File A and File B use different column names for the same data (e.g. Email vs EmailAddress, or CustomerID vs ID), use the Column Mapping section to define the equivalences. Click Auto-suggest to automatically detect columns with similar names.

⭐ Export Options

After comparing, you can download:

  • Changed rows CSV — modified rows showing old and new values side by side
  • Added rows CSV — rows only found in File B
  • Removed rows CSV — rows only found in File A
  • Unchanged rows CSV — identical rows across both files
  • Full comparison CSV — all rows with a _diff status column
  • JSON report — a structured JSON report including summary statistics and all diff categories

⚠️ Duplicate Key Warning

If the selected key column(s) contain duplicate values in either file, the tool will display a warning. Duplicate keys can cause incomplete or ambiguous matching results. Consider using multiple key columns together (e.g. FirstName + LastName + Email) to ensure uniqueness.

⭐ Privacy & Security

All CSV comparison processing runs entirely in your browser using JavaScript. Your data is never uploaded to any server and never leaves your device. This makes the tool safe to use with sensitive data such as customer records, financial reports, or HR exports.

This tool is also known as

  • compare two csv files online
  • find differences between csv files
  • csv diff tool free
  • compare csv rows and columns
  • csv file comparison checker

Frequently Asked Questions

This tool compares two CSV files and identifies added rows, removed rows, modified rows, and unchanged rows. It also provides cell-level difference details showing exactly which values changed between the two files.

Upload or paste your CSV data into the File A (original) and File B (updated) panels, choose a comparison mode, configure any ignore options, and click Compare. Results appear instantly in colour-coded tabs showing each diff category.

There are three comparison modes. Key Column mode matches rows using one or more unique identifier columns, such as an ID or email address. Row-by-Row mode compares records by their position in the file. Full File mode treats each row as a unique signature and finds records unique to each file regardless of order.

Key Column comparison matches rows across the two files using a selected identifier column, such as CustomerID or Email. This is the most reliable mode for real-world data where the row order may differ between exports. Select one or more columns as key identifiers before clicking Compare.

Yes. Use the Column Mapping section to map columns with different names between File A and File B. For example, you can map 'Email' in File A to 'EmailAddress' in File B. Click Auto-suggest to automatically detect columns with similar names.

Yes. The Cell Differences tab shows a detailed breakdown of every changed cell, including the row identifier, the column name, the old value from File A, and the new value from File B.

You can ignore case differences, leading and trailing whitespace, row order, column order, and treat empty values as null. These options help avoid false positives when comparing data with minor formatting differences.

Yes. The filter bar above the results lets you search by keyword and filter by a specific column. This is useful when working with large datasets where you only need to review a subset of differences.

You can export changed rows, added rows, removed rows, or unchanged rows as separate CSV files, or download a full comparison CSV that includes all rows with a status column. A JSON report is also available with summary statistics and all diff categories.

If duplicate values are detected in the key column(s), the tool shows a warning. Duplicate keys can lead to incomplete or ambiguous matching. To improve accuracy, consider selecting multiple columns together as a composite key.

Yes. The tool automatically detects whether your CSV uses commas, semicolons, tabs, or pipes as delimiters by analysing the first line. You can also manually select the delimiter in the options panel.

No. All processing happens entirely in your browser using JavaScript. Your CSV data is never sent to any server and never leaves your device, making this tool safe for sensitive or confidential data.

Yes. The tool processes data efficiently in memory and uses chunked rendering to handle large files. For very large files, using key column mode is recommended as it builds an indexed map for fast lookup.

The tool supports UTF-8, Windows-1252, ISO-8859-1, and UTF-16. Select the encoding in the options panel before uploading a file to ensure special characters are correctly interpreted.

Yes. You can paste CSV text directly into either text area. The tool processes pasted content the same way as uploaded files and displays column and row counts immediately after pasting.

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