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Duplicate Line Checker

Find which lines repeat in a list, and where they are.

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Duplicated line Times On lines

Quick Tool Overview

The Duplicate Line Checker reports duplicates rather than removing them: every repeated line is listed with its occurrence count and the exact line numbers it appears on, which is what you need when you are diagnosing a data problem rather than tidying a file.

What it does
Finds duplicate lines and reports where they are
You give it
An import file, export, mailing list or any set of lines
You get back
Each repeated line with its count and line numbers
Best for
Diagnosing data problems and auditing imports
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About the Duplicate Line Checker

Removing duplicates is easy. Finding out which ones were duplicated, how many times, and on which lines is the part that actually matters when you are investigating a data problem rather than just cleaning it up.

This reports rather than removes. Every line that appears more than once is listed with its occurrence count and the line numbers it appears on, so a duplicated email address in an import file can be traced back to both rows. Comparison can ignore case, leading and trailing whitespace, and a chosen column of a delimited file — that last one being how you find rows sharing an ID even when the rest of the row differs.

Key features of the Duplicate Line Checker

Reports rather than removes

You get the line numbers of every collision, which a de-duplicating tool throws away.

Column-based comparison

Compare only one field of a delimited row to find records sharing an ID even when the rest differs.

Case and whitespace folding

Catch the duplicates that differ only by capitalisation or a trailing space.

Unique list too

The entries that appear exactly once are listed separately, which is often the half you actually want.

Scales to large files

Hash-based counting rather than nested comparison, so tens of thousands of lines stay fast.

How to use the Duplicate Line Checker

  1. 1

    Paste your list

    An import file, an export, a mailing list or any set of lines.

  2. 2

    Set the comparison rules

    Ignore case and surrounding whitespace, or compare only one column of a delimited file.

  3. 3

    Read the duplicate report

    Each repeated line is shown with its count and the exact line numbers it appears on.

  4. 4

    Copy what you need

    The duplicate list, the unique list and the line numbers can each be copied separately.

Frequently asked questions

No, it reports them. That is the point — when you are diagnosing a data problem you need to know which rows collided and where, not just get a shorter file. Use the Duplicate Line Remover when you want them gone.

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