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ListDiff

Find duplicates in a list

Paste one list. See which values repeat, how often, and on which lines—then copy a unique list. The scan stays in your browser.

Free Local processing No signup Counts & line numbers

Tool

List
0 lines
Updates as you type

Paste a list—repeats and counts appear automatically.

Comparing two lists for missing vs extra items? Use the list compare tool. Merging two sources into one unique set is the Union tab.
Compare lists Merge two lists Compare CSV Guide Docs

How it works

  1. Paste one item per line—or try Example.
  2. Leave Trim and Ignore case on unless you need exact spelling.
  3. Read the duplicate table: value, count, line numbers.
  4. Copy the unique list (first occurrence kept) or the TSV report.

Good for

  • Email or username exports before a send or import.
  • SKU files that should be unique but were pasted twice.
  • Cleaning a column copied from Excel.
  • Checking a list before you trust a two-list compare.

Quick answers

Count vs lines? Count is how many times the value appears. Lines are 1-based positions in the paste.

Need missing vs extra? That is list compare (two boxes), not this page.

Need a merged unique set from two sources? Use the Union tab.

What is this tool?

A free duplicate finder for a single list. It does not compare two files against each other. The two-list tool still has a Dupes in A / Dupes in B tab when you already have both sides open.

Step-by-step notes live in the find duplicates guide if you are using the main list tool instead.

Related tools

Compare lists

A only / B only / Intersection after you have two lists.

Compare CSV

Join two tables by key; duplicate keys are warned there too.

Merge without duplicates

Union of two sources into one unique set.

FAQ

How do I find duplicates in a list online?

Paste above. Repeated values show with counts and line numbers—nothing is uploaded for the scan.

How do I get a unique list?

Click Copy unique list. The first time each value appears is kept, in original order.

Is this the same as comparing two lists?

No. Use list compare for items only in A or only in B.