Duplicate Line Counter
Count extra copies of repeated entries in a list and see how many unique entries remain. Choose case-sensitive matching when capitals matter.
How to use Duplicate Line Counter
1. Paste or type your text or list into the box. 2. Choose any options shown, then select Count. 3. Select Copy result to copy the answer. 4. Select Reset to clear the box and start again.
Why use this tool?
Check how much a repeated list would shrink before removing duplicates. The extra-copy total and the unique-entry total answer two different questions.
How the calculation works
Duplicate occurrences = sum(max(count per normalised key − 1, 0)); also count unique keys. Entries are non-empty trimmed lines. Blank lines are ignored; repeated entries remain separate row slots unless the tool explicitly removes duplicates. Commas inside a line are retained. Case sensitivity is selected. A repeated value counts additional occurrences beyond its first row, not the number of repeated keys.
Example
Worked example: Lines = "A\na\nB"; Case Sensitive = false. Result: Duplicate occurrences: 1 Unique values: 2.
Practical tip
Use Duplicate Line Finder to inspect which entries produced the duplicate count.
Frequently asked questions
What does Duplicate occurrences mean?
It counts copies beyond the first occurrence. A value listed three times contributes two duplicate occurrences.
Are blank lines included?
No. Blank lines are ignored and spaces at the ends of entries are trimmed. Turn case-sensitive matching on if differently capitalised entries should remain distinct.
How do I copy the result or start again?
Select Copy result after running the tool to copy the displayed answer. Reset clears the text and result, so keep a separate copy of any text you want to save.