List Comparator
Find what is in both lists, in one but not the other, or in either.
What Is in Both Lists, and What Is Not
Two exports that should match and do not. A subscriber list against an attendee list. Yesterday’s inventory against today’s. The question is always one of four: what is in both, what is only in the first, what is only in the second, or what is in either.
Doing this in a spreadsheet means a VLOOKUP and a filter and a fair chance of getting it subtly wrong. Doing it here takes one paste each.
Key features
- All five views — in both, only A, only B, in either, and in one but not the other.
- Counts at a glance — the four totals update as you type, before you pick a view.
- Case handling — case-insensitive by default, because exported data rarely agrees on capitalisation.
- Whitespace tolerance — trailing spaces from a spreadsheet paste do not create false differences.
- Set semantics — duplicates within one list count once, so the totals describe the sets rather than the lines.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: List Comparator
- Paste list A
One entry per line. - Paste list B
The four counts appear immediately. - Choose a view
In both, only in one, in either — whichever question you actually have. - Copy the result
Sorted by default, ready to paste back into a spreadsheet.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Text |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Does it compare whole lines or individual words?
Whole lines. An entry is whatever is on one line, which is how exported data arrives. To compare fields within a line, split the data first with our CSV tools.
Why do my counts not add up to the number of lines I pasted?
Because duplicates within a single list count once. Ten lines with three repeats is seven entries. That is what makes the comparison a set operation rather than a line count.
Should I turn on case sensitivity?
Usually not. Data exported from two different systems rarely agrees on capitalisation, and a case-sensitive comparison would report "Smith" and "SMITH" as different people. Turn it on when case genuinely carries meaning, as in code identifiers.
Is there a size limit?
No hard limit — the comparison runs in memory using hash maps, so tens of thousands of lines per side are instant.