Duplicate Highlighter

Two Modes: Highlight vs. Remove

Highlight Duplicates visually marks repeated lines in your text so you can review them before deciding what to keep. This mode is ideal when you want context before deletion.

Remove Duplicates immediately strips all repeated lines, keeping only the first occurrence of each unique entry. This mode is perfect for rapid list cleanup.

Common Use Cases

• Email list hygiene — remove repeated subscriber addresses before a campaign send.
• CSV deduplication — paste a column from a spreadsheet, clean it, paste it back.
• Code review — check for accidentally duplicated import statements or CSS rules.
• Data normalization — ensure unique entries in lookup tables or config files.

How to Use the Duplicate Highlighter

Paste your text with one item per line, then choose what you want to do. Highlight Duplicates shows your text with repeats marked so you can review them first, while Remove Duplicates returns a clean list with repeated lines deleted. Use Copy result to take the output with you. Nothing is changed in the input box, so you can try both buttons on the same text.

What Gets Marked

• Repeated lines are highlighted in red across the whole line. A line counts as a repeat when another line matches it once capitalization and spaces at the start and end are ignored.
• Repeated words are highlighted in yellow wherever a word appears two or more times anywhere in your text, which helps you spot words you lean on.

A Worked Example

Suppose your list looks like this:

Remove Duplicates keeps the first occurrence of each line and returns Red, blue, Green. "red " (with a trailing space) matches "Red", and "Blue" matches "blue", so both are dropped. Note that the version that survives is always the first one, so "Red" keeps its capital letter.

Things to Keep in Mind

• Only whole lines are compared. "red cat" and "red cat" (with two spaces) are different lines. Run the text through the Whitespace Cleaner first if you suspect hidden spacing differences.
• The original order of your list is preserved. If you want it sorted afterwards, use the Line Sorter.
• Highlighting is for review only. Highlight first if the list matters, so you can check what will be removed before you commit to it.

Common Uses

• Cleaning a mailing list or a column of IDs pasted from a spreadsheet.
• Merging two keyword lists and removing overlaps.
• Checking a to-do list, reading list or set of tags for accidental repeats.

Frequently Asked Questions

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