CSV Deduplicator & Diff Tool
Compare CSVs securely in your browser to find matching or missing rows instantly without macros or formulas.
Compare two CSV files or lists to find common, unique, or missing data.
A powerful local tool to find the intersection (duplicates) and difference between two datasets. Just copy and paste two lists or upload CSVs to instantly discover identical rows, unique items, or combine them into a deduplicated master list.
How this page is maintained
- Steps and copy are checked against the current tool behavior.
- Browser limits, file-size constraints, or compatibility gaps are documented when relevant.
- Unless a page explicitly says otherwise, files and text stay in the browser during processing.
Stop Doing VLOOKUP Manually
Matching two datasets to find out who didn't pay, or which emails bounced, usually involves fighting with Excel formulas like VLOOKUP or INDEX MATCH.
Our CSV Diff Tool aims to solve the 90% use case of data merging: Finding out what's the same, what's missing, and combining lists cleanly.
Setup and Go
Simply paste in your "Base" list into the left block, and your "Compare" list into the right. We automatically detect common columns if you provide headers. You can then quickly hunt down:
- Intersection (In Both): The exact rows that mirror each other across both lists.
- Difference (Only in A): Find out what records only exist in the primary list and are missing from the secondary.
- Union (Deduplication): A life saver when you have two slightly overlapping contact lists and you need a single, deduplicated master file.
The entire procedure costs 0 server requests. Your financial or customer intelligence stays completely local.
Key features
- Instant Comparison: Skip VLOOKUP formulas. Just paste two lists and instantly see what is missing or duplicated.
- Zero Uploads: All comparison logic runs entirely in your browser using PapaParse. Your sensitive business intelligence stays local.
- Multiple Modes: Support for Intersection (A∩B), Difference (A-B, B-A), and Deduplicated Union (A∪B).
- Column-Specific Matching: Have a primary key? Choose exactly which column to lock on for precise enterprise-grade data merging.
Frequently asked questions
Wait, does my spreadsheet leave my computer?
Not at all. We process the text using local browser memory. Nothing is ever uploaded to any database or external server.
Can I just paste email lists instead of a full CSV?
Yes! It effortlessly handles single-column text logic. Just uncheck the "First row is header" if it's a raw list, paste them in, and hit compare.
What is a Deduplicated Union?
It combines both of your lists but automatically strips out any duplicates across them, granting you one clean master list.