List Comparator (Diff)

How it Works

List Comparator is a free online tool that supports text pasting and Excel/CSV file uploads. It uses set theory algorithms to compare two lists (or datasets) and quickly find their intersections, unions, and differences.

Intersection: Items that appear in both List A and List B.
A Only (A - B): Items present in A but not in B.
B Only (B - A): Items present in B but not in A.
Union: All unique items from both lists combined.

This tool runs entirely in your browser. No data is uploaded to any server, ensuring your privacy.

Use Cases

SEO Keyword Analysis

Compare two keyword lists to find common value words (Intersection) or discover missing long-tail opportunities (A/B Only).

Email List Cleaning

Exclude an "Unsubscribed" list from your "Send" list (Difference) to ensure compliance and improve delivery rates.

Data Verification

Compare old and new database exports to identify added, lost, or modified records to ensure data integrity.

Dependency Management

Compare `package.json` dependency lists or file manifests between environments to check for missing libraries.

FAQ

What is the file size limit?

Since all processing happens locally in your browser, the limit depends on your device's memory. Typically, CSV or Excel files with tens of thousands of rows are processed instantly. Files larger than 50MB might cause a brief freeze.

Which file formats are supported?

We support Plain Text (.txt), CSV (.csv), and Excel (.xls, .xlsx) files. For Excel files, the tool automatically reads the first non-empty column of the first sheet.

Why did my Excel file only import one column?

This is a "List" comparator. If your Excel file has multiple columns, we prioritize the first one. We recommend organizing your data in a single column or pasting specific columns directly into the text area.

How do I ignore case sensitivity?

Simply uncheck the "Case Sensitive" box in the control panel. "Apple" and "apple" will then be treated as the same item.

Is my data safe? I'm comparing sensitive lists.

Yes, absolutely. This tool is a 100% client-side application. All calculations happen purely within your browser, and no data is ever uploaded to our servers. You can even disconnect from the internet while using that tool for extra security.

What happens if there are duplicates in the same list?

This tool treats lists as mathematical Sets. This means duplicates within a single list are automatically removed before comparison. For example, if List A contains "Apple" twice, it will count as just one "Apple" during the comparison process.

How can I save or export the results?

We provide a convenient "Copy" button at the bottom-right of each result box (e.g., "A Only" or "Intersection"). Clicking it will copy the content to your clipboard, allowing you to paste it cleanly into Excel, Google Sheets, or any text editor.

Does the order of items matter?

No. The Intersection, Union, and Difference calculations are based on whether an item *exists* in the list, not where it is located. So even if your two lists are sorted differently, the comparison results will be accurate.

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A Only (A - B)

B Only (B - A)

Intersection (A ∩ B)

Union (A ∪ B)