Duplicate extractor
Find the items that repeat in a list and show value, count and occurrence positions — with case and whitespace folding, a unique-only mode, plus totals, unique count and duplicate group stats.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Result
One item per line, ready to copy.
Paste a list to find duplicates
Total: 0 · Unique: 0 · Repeats: 0 · Duplicate groups: 0
What this tool does
- See which people were registered twice after merging two lists, with row numbers for lookup.
- Spot duplicated IDs in an export before they collide on a primary key.
- Use the unique-only mode to get the items that appear exactly once.
Example
Input
apple banana apple cherry banana apple
Output
apple 3 banana 2
apple appears three times (rows 1, 3, 6) and banana twice; cherry shows up once so it is not a duplicate.
Frequently asked questions
Is Apple the same as apple?
Not by default. With “Ignore case” on they count as one item and the first spelling is kept, without forcing it to lower case.
Do leading or trailing spaces matter?
They are ignored by default, since exported sheets often carry invisible trailing spaces. Turn “Ignore leading/trailing whitespace” off for strict comparison, where “a ” and “a” become two items.
Is each duplicate listed once?
Yes. One row per duplicated value holds the count and every occurrence position, so 500 repeats of one value still produce a single row.
Can I see only the unique items?
Yes. Switch “Output” to “Unique items only” to get the entries that appear exactly once; “Everything” lists all entries in first-seen order with their counts.
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