How to compare two lists online

Last updated: 2026-08-02

A simple method for comparing 2 lists—plain text, IDs, usernames, or columns from a spreadsheet—so you spend less time chasing false mismatches.

Five steps that work for most lists

Open the compare tool and fill both lists.
Start with the defaults: case-insensitive, trim spaces on, skip blank lines on.
Only turn on line-splitting or CSV parsing if a single line holds several values.
Compare, then check A only, B only, and Intersection.
Copy or download the tab you need as TXT or CSV.

Which settings should I try?

Turn case sensitive on only if ABC and abc should count as different.
Leave trim spaces on for anything pasted from a spreadsheet or typed by hand.
Leave skip blank lines on unless empty rows mean something in your process.
Turn dedupe on for a final unique-item compare; leave it off first if you want to see repeats inside each list.

Try this example

List A: u001, u002, u002
List B: u002, u003
Settings: trim on, skip blanks on, dedupe off
Result: A only = u001, B only = u003, both = u002, and A shows a duplicate u002.

Common mistakes

Low overlap even though the lists look alike—check letter case and spaces first.
Counts look huge—you may be splitting lines or treating CSV rows differently than you meant to.
Line count and unique-item count disagree—blank lines inflate the line count.

FAQ

What is the fastest way to compare two lists?

Paste or import both lists, keep the defaults, compare, then check only in A, only in B, and both.

Why do two similar lists show low overlap?

Usually case, spaces, blank lines, or how multi-value lines were split.