Remove duplicate lines from text. Case-sensitive or case-insensitive, keep order or sort.
The Duplicate Line Remover strips repeated lines from any block of text, keeping only the first occurrence of each unique line. It supports case-sensitive and case-insensitive matching, optional whitespace trimming, blank-line removal and alphabetical sorting of the result. The tool processes everything locally in your browser, making it fast and private for handling sensitive data.
The tool keeps the first occurrence of each unique line and discards all subsequent duplicates, preserving the original order of your list by default. Internally it uses a JavaScript Set to track lines already seen, making lookups O(1) and the overall process linear in the number of lines - even very large lists are processed near-instantly. If you enable the "Sort result" option, the deduplicated lines are then sorted alphabetically using locale-aware comparison.
All processing happens entirely in your browser - no text is sent to any server, stored, or logged. This means you can safely paste email lists, customer records, API keys or any other sensitive data without privacy concerns. When you close the tab or refresh the page, all pasted content is gone.
With case-sensitive matching enabled (the default), "Apple" and "apple" are treated as two different lines and both are kept. When you disable case-sensitive matching, the comparison is done on the lowercased version of each line, so "Apple", "APPLE" and "apple" are all treated as the same entry - only the first occurrence (in its original casing) is retained. Use case-insensitive mode when your data may have been entered or exported with inconsistent capitalization.
The tool has no built-in line limit and can handle lists of tens of thousands of lines without issue on any modern computer. The bottleneck is your browser's available memory rather than the tool itself. For extremely large files (hundreds of thousands of lines), consider using a command-line utility such as sort -u on Linux/Mac or PowerShell's Get-Content | Sort-Object -Unique on Windows for faster processing.
Excel's "Remove Duplicates" feature works on columns in a structured table and requires importing your data into a worksheet. This tool is faster for plain text lists - you paste, click and copy in seconds with no formatting or import steps. It also gives you additional controls like whitespace trimming and blank-line removal that are tedious to replicate with spreadsheet formulas, and it produces a clean text output that can be pasted directly back into code or a database query.