List Comparison Tool
Paste one list in each box, one item per line, and click Compare. You get three lists back — the items in both, the items only in List A, and the items only in List B — each with a count and its own copy button. Free, no sign-up, and nothing leaves your browser.
How to Use the List Comparison Tool
- Paste the two lists. One item per line in each box. Blank lines are ignored.
- Set the options. Case-insensitive, Trim whitespace and Ignore duplicates are all on by default; the next section explains what each one changes.
- Click Compare. A sentence summarises both lists and the overlap, and three boxes show In both, Only in A and Only in B.
- Copy what you need. Each box has its own Copy button, so you can take the missing items straight to a new list or a spreadsheet.
What the Three Results Mean
| Result | In set notation | It answers |
|---|---|---|
| In both | A ∩ B (intersection) | Which items are on both lists? |
| Only in A | A − B (difference) | What is on A that B is missing? |
| Only in B | B − A (difference) | What is on B that A is missing? |
Add all three together and you have the union, every distinct item across both lists. Items keep the order of the list they came from, and nothing is sorted. The In both box is taken from List A, so if the two lists spell an item with different capitals, the List A spelling is the one shown.
What the Options Change
- Case-insensitive treats "Jones 2020" and "jones 2020" as the same item. Turn it off when capitalisation carries meaning, as in case-sensitive IDs or codes.
- Trim whitespace strips spaces and tabs from both ends of every line before comparing. Leave it on: a trailing space from a copy and paste is the commonest cause of an item showing up as different when it is not.
- Ignore duplicates keeps one copy of an item that is repeated within a list. With it off, repeats stay in the lists and the counts include them.
A Worked Example
Suppose List A is the sources you cite in your text and List B is your reference list:
List A (in-text citations)
Smith 2019 Jones 2020 Lee 2018 Garcia 2021 Khan 2017
List B (reference list)
jones 2020 Lee 2018 Patel 2022 Smith 2019 Smith 2019
| Settings | In both | Only in A | Only in B |
|---|---|---|---|
| Defaults | Smith 2019, Jones 2020, Lee 2018 | Garcia 2021, Khan 2017 | Patel 2022 |
| Case-insensitive off | Smith 2019, Lee 2018 | Jones 2020, Garcia 2021, Khan 2017 | jones 2020, Patel 2022 |
With the defaults, List A has 5 items and List B has 4, because the repeated Smith 2019 was collapsed. Three items match. The two items only in A, Garcia 2021 and Khan 2017, are cited in the text but missing from the reference list; the one item only in B, Patel 2022, is listed but never cited. That is the two-way check a final proofread needs. Switch Case-insensitive off and the picture changes: jones 2020 no longer matches Jones 2020, so it shows up as a difference on both sides.
Common Mistakes
- Expecting fuzzy matching. Items match only when they are identical after the options are applied. "Smith, J." and "J. Smith" are different items, and so is a spelling with a typo. Put both lists in the same format first.
- Pasting a table. If each line holds several columns, a change in any column makes the whole line different. Compare one column at a time; the Column Extractor pulls a column out.
- Reading the order as meaningful. This tool compares sets of items, not positions. To see where a line was inserted or moved in a document, use the Text Diff Checker.
Which Tool Do You Need?
| If you want… | Use |
|---|---|
| What two lists share and where they differ | This page |
| Two lists combined into one, side by side or in sequence | List Merger |
| Repeated lines removed from a single list | Remove Duplicate Lines |
| Changes between two versions of a text, highlighted in place | Text Diff Checker |
| Only the lines that contain a word or pattern | Line Filter |
Frequently Asked Questions
- How do I compare two lists online?
- Paste one list into List A and the other into List B, one item per line, and click Compare. The results show the items in both lists, the items only in A and the items only in B, each with a count and a copy button.
- How do I find the items that are in one list but not the other?
- Run the comparison and read the Only in A box for items missing from B, or Only in B for items missing from A. To find what B lacks, put the complete list in A and the shorter one in B.
- Is the comparison case-sensitive?
- Not by default: "Apple" and "apple" count as the same item. Switch Case-insensitive off if capitalisation matters, for example when comparing codes or usernames.
- What does Trim whitespace do?
- It removes spaces and tabs from the start and end of every line before it compares, so "apple " matches "apple". It is on by default because stray spaces from copy and paste are a very common cause of false differences. It does not touch spaces in the middle of an item.
- How are duplicate items handled?
- With Ignore duplicates on, repeats within a list are collapsed to one, so each item appears once in the results and the counts are of distinct items. Turn it off to keep every occurrence from the lists.
- Is there a limit on list length?
- There is no set limit. The comparison runs in your browser, so very long lists are bounded only by how much your device can handle.
- Is my data uploaded?
- No. Both lists are compared in your browser and are not sent or stored.