Find, count, and remove repeated lines from lists, CSV rows, logs, and text documents instantly. Customize case sensitivity, whitespace normalization, sorting, and frequency analysis—100% privately in your browser.
Intelligent line deduplication & frequency analysis utility
The Remove Duplicate Lines tool is a high-performance, free online utility that scans your text line by line to identify and eliminate repeated entries. Whether you are cleaning a data list, deduplicating email addresses, tidying up code output, or processing log files, this tool gives you precise control over how duplicates are handled.
It offers four removal modes, flexible comparison options (case sensitivity, whitespace handling, accent-insensitive matching, blank-line controls), post-processing sort/shuffle capabilities, and a detailed frequency report. All processing runs 100% locally inside your browser for complete privacy and instant speed.
Common scenarios where duplicate entries cause issues
Spreadsheet exports, CSV files, and database dumps often contain repeated rows that need deduplication before analysis.
Mailing lists and contact exports frequently have duplicate addresses that inflate counts and cause double-sends.
Duplicate import statements, repeated CSS rules, or redundant config lines clutter codebases and cause conflicts.
Server logs and error reports contain repeated entries that obscure unique issues and slow debugging.
Keyword lists, tag collections, and editorial notes accumulate duplicates during collaborative editing.
Training data, prompt templates, and automation scripts must be deduplicated to avoid bias and wasted processing.
Built for speed, flexibility, and precision
Keep first occurrence, keep last occurrence, remove all duplicates, or extract duplicates only.
Treat 'Apple' and 'apple' as identical or distinct lines with one click.
Trim edges, collapse internal spaces, and match accented characters (café / cafe).
Compare normalized versions while outputting the original line formatting untouched.
Sort A→Z, Z→A, shortest first, longest first, reverse, randomize, or number lines.
See exactly which lines are duplicated, how many times each appears, and download the report.
Copy to clipboard or download as TXT, CSV, JSON, or Markdown (.md).
Up to 50 snapshot states with standard Ctrl+Z / Ctrl+Shift+Z shortcuts.
Zero server calls. Your text data never leaves your browser.
Tailored for professionals and everyday text tasks
Deduplicate datasets, CSV exports, and query results before importing into analytical platforms.
Clean up log files, remove redundant imports, and normalize configuration entries.
Deduplicate keyword lists, email campaigns, and audience segments.
Remove repeated headings, bullet points, and notes from collaborative drafts.
Clean reference lists, bibliographies, and extracted data from multiple sources.
Validate unique entries in SQL dumps and bulk data exports.
How comparison options affect which lines are treated as duplicates
Lines are compared after converting to lowercase. “Apple”, “apple”, and “APPLE” are treated as the same line.
Apple → kept
apple → removed
APPLE → removed
Lines are compared exactly as written. Different capitalizations are treated as distinct lines.
Apple → kept
apple → kept
APPLE → kept
Use Remove Duplicate Words to scan word-by-word within sentences and paragraphs.
Simple 5-step workflow to deduplicate your text
Paste text or drag & drop a .txt file into the input box.
Select Keep First, Keep Last, Remove All, or Duplicates Only.
Configure case sensitivity, whitespace, and sort preferences.
Check the output, statistics, and duplicate frequency report.
Copy to clipboard or download as TXT, CSV, JSON, or Markdown.
See how each mode handles different duplicate scenarios
Apple Banana Apple Orange Banana Mango
Apple Banana Orange Mango
Apple Banana Apple Orange Banana Mango
Apple Orange Banana Mango
Apple Banana Apple Orange Banana Mango
Orange Mango
Apple apple APPLE Banana
Apple Banana
Cherry Apple Banana Apple Cherry
Apple Banana Cherry
Your data stays on your device
All text processing occurs entirely in your web browser. Your text is never transmitted to any server, never stored in any database, and never logged or analyzed. Close the browser tab and your data is completely gone—making this tool safe for sensitive, confidential, and proprietary lists.
Everything you need to know about duplicate line removal
It scans your text line by line, identifies lines that appear more than once, and removes the duplicates based on your chosen mode. You can keep the first occurrence, keep the last occurrence, or remove all lines that have any duplicates.
Keep First preserves the earliest appearance of each line and removes later duplicates. Keep Last preserves the latest appearance and removes earlier ones. Both reduce the text to unique lines but in different order.
Remove All Duplicates eliminates every line that appears more than once in the text, keeping only lines that appear exactly once. For example, if 'Apple' appears 3 times, it is removed entirely from the output.
By default, the tool ignores case differences. So 'Apple', 'apple', and 'APPLE' are treated as the same line. Only the first (or last) occurrence is kept. Enable Case-sensitive comparison to treat them as distinct lines.
Yes. When Trim whitespace is enabled (default), leading and trailing spaces are stripped before comparison. So ' Apple ' and 'Apple' are treated as duplicates. The original formatting is preserved in the output when Preserve formatting is on.
Normalize spaces collapses multiple consecutive spaces and tabs within a line into a single space before comparing. So 'Hello World' and 'Hello World' are treated as the same line.
By default, repeated blank lines are deduplicated: the first blank line is kept and later blanks are removed. Enable Preserve all blank lines to keep every empty row (for paragraph spacing). Use Remove blank lines to delete all empty lines from the final output. These options are separate: deduplicating blanks is not the same as removing every blank line.
This tool compares entire lines (split on line breaks). The Remove Duplicate Words tool compares individual words within the text. Use line deduplication for lists, logs, and URLs; use word deduplication for prose, tags, and keyword lists.
Yes. The Sort & Order panel lets you sort alphabetically (A→Z or Z→A), by line length (shortest or longest first), reverse the order, randomize (shuffle), or add line numbers to the output.
The Duplicate Report shows a frequency table listing every line that appears more than once, along with its count. It also summarizes total lines, unique lines, duplicates found, duplicate percentage, and the largest duplicate group. You can download the report as a text file.
Yes. The processing engine uses Map-based O(1) lookups for duplicate detection, making it efficient for 200,000+ lines. All processing runs client-side in your browser with no server round-trips. File uploads are supported up to 5MB.
Absolutely. All processing happens entirely in your browser. Your text is never sent to any server, never stored, and never logged. Close the tab and your data is gone. No cookies or tracking of text content are involved.
You can copy the result to clipboard, or download as plain text (.txt), CSV (.csv with proper quoting), JSON (.json with a lines array), or Markdown (.md). You can also print or use the native share functionality.
Yes. The tool includes full undo/redo for input changes. Press Ctrl+Z (Cmd+Z on Mac) to undo, and Ctrl+Shift+Z to redo. Up to 50 history states are preserved. Use Reset All to clear everything.
When enabled (default), the tool compares normalized versions of lines internally (trimmed, case-folded, spaces collapsed as configured) but outputs the original text with its exact spacing and casing intact. Disable it to output the normalized version.
Yes. The interface is fully responsive and works on smartphones and tablets. You can paste text, upload files, and use all features on any device with a modern web browser.
