Remove Duplicate Lines
Remove duplicate lines from any list — keeps the first occurrence of each unique line and preserves order. Free, instant, client-side deduplicator.
🔒 100% Client-Side Processing
Your data is processed entirely in your browser and never transmitted to any server.
0 / 100M Limit
Common Use Cases
Cleaning mailing lists
Remove repeated addresses after merging signup exports so nobody receives the same campaign twice.
Merging data exports
Combine two CSV extracts or log pulls and drop the overlapping rows before analysis.
Deduplicating keyword lists
Collapse repeated terms after combining keyword research from several tools into one master list.
Frequently Asked Questions
- Does deduplication preserve the order of my list?
- Yes — the tool keeps the first occurrence of each unique line in its original position and drops later repeats, using a JavaScript Set. Nothing is sorted or rearranged.
- Is the duplicate comparison case-sensitive?
- Yes — "Apple" and "apple" count as different lines, and so do lines with trailing spaces. Normalise case with the Lowercase Converter and strip stray whitespace first for aggressive deduplication.
- Does trailing whitespace stop duplicates from matching?
- Yes, and this is the most common surprise. Two lines that look identical but differ by a trailing space are different strings, so both survive. Data pasted from a spreadsheet or a PDF frequently carries invisible trailing spaces — clean it with Remove Whitespace first if the result looks wrong.
- How do I find out which entries were duplicated?
- This tool reports what remains, not what was removed. To see the counts before you strip anything, run the list through the Word Frequency Counter, which shows how many times each value appeared — useful when the duplicates themselves are the finding rather than the noise.
- Should I sort before or after deduplicating?
- Deduplicate first if you want to keep the original order of first appearance, since sorting destroys it. Sort first if you would rather review the duplicates yourself — Sort Lines Alphabetically puts identical entries next to each other, so they are visible before anything is discarded.
- Is my data private when I use this tool?
- Yes. This tool runs entirely in your browser using client-side JavaScript — nothing you type is transmitted to, logged by, or stored on any server. You can safely process confidential text, tokens, or code.