Remove Duplicate Lines

Paste text and instantly remove all duplicate lines. Supports case-insensitive matching, line trimming, and blank line removal.

Input

Options

Case-insensitive matching

Trim whitespace from lines

Remove blank lines

Frequently Asked Questions

Yes. The first occurrence of each unique line is kept and its position is preserved. Subsequent duplicate occurrences are removed. The output order matches the order of first appearance in the input.

When enabled, Apple and apple are treated as the same line and the first occurrence is kept. When disabled (default), case differences are significant — Apple and apple would both be retained.

When enabled, leading and trailing spaces are stripped from each line before comparison and from the output. This means apple and apple would be treated as duplicates of apple.

A duplicate is any line whose content is identical to a previously seen line after applying your chosen options (trimming and case folding). Only the first occurrence is kept; all later occurrences are removed. If case-insensitive is off, "Apple" and "apple" are not duplicates. If trimming is off, "apple " (with trailing space) is not a duplicate of "apple".

In data cleaning workflows, duplicate rows inflate counts, skew statistics, and cause double-billing or double-sending issues. Removing duplicates from email lists prevents sending the same message twice to the same person. Removing duplicate IDs from exports ensures accurate record counts. Enable case-insensitive and trim options to catch near-duplicates introduced by inconsistent data entry.

This tool keeps the first occurrence and removes all subsequent duplicates. This is the most common behavior and matches what SQL's DISTINCT, Python's dict.fromkeys(), and spreadsheet deduplication tools do by default. If you need to keep the last occurrence instead, reverse the list first, remove duplicates, then reverse again.

No. This tool performs exact matching only (with optional case-folding and trimming). Near-duplicates like "John Smith" and "John Smit" (a typo) would not be flagged. Fuzzy deduplication requires a similarity algorithm such as Levenshtein distance or Jaro-Winkler, which are typically implemented in Python libraries like fuzzywuzzy or rapidfuzz.

When Remove blank lines is checked (the default), all empty lines are removed from the output. When unchecked, blank lines are treated as a line with empty content — meaning multiple blank lines would be deduplicated down to a single blank line. If you want to preserve intentional paragraph spacing, uncheck this option.

In case-sensitive mode (default), "Apple", "apple", and "APPLE" are three distinct lines — all three would be kept. In case-insensitive mode, all three are considered duplicates of the same value and only the first occurrence is kept. Use case-insensitive mode when cleaning user-submitted data where the same value may have been entered with different capitalization.

Not exactly. The Unix command sort -u sorts the lines alphabetically and then removes duplicates — it does not preserve the original order. This tool removes duplicates while preserving the original line order (keeping the first occurrence). If you also want alphabetical sorting, use the Sort Lines tool after deduplication.

About This Duplicate Line Remover

This free duplicate line remover deletes repeated lines from any text, keeping only the first occurrence of each line. Options include case-insensitive matching and trimming whitespace before comparing — all processing happens in your browser.

When to use this tool

Deduplicating a list of URLs, email addresses, or keywords
Cleaning up log output with repeated identical lines
Removing duplicate entries from a CSV column before importing
Normalising a word list before further text processing

Standards & References

Wikipedia — Duplicate Elimination

How It Works

Paste Your List

Paste a list of items, one per line, into the textarea. The tool processes each line independently.

Set Options

Choose case-insensitive matching, trim whitespace before comparing, and whether to remove blank lines from the output.

Get Unique Lines

Click Run and see how many lines were removed. Copy the deduplicated output with one click.

Common Use Cases

Email List Cleanup

Deduplicate newsletter subscriber exports before importing to a CRM. Duplicate email addresses increase bounce rates and waste send quota.

SEO Keyword Research

Remove repeated keywords when merging exports from multiple tools like Ahrefs, SEMrush, and Google Search Console into a single master list.

Log File Processing

Deduplicate repeated log entries to surface unique error messages and warnings, making it faster to identify distinct failure modes.

CSV Data Cleaning

Remove duplicate rows from exported reports before analysis. Clean data prevents skewed metrics and double-counting in aggregations.

Code Import Statements

Clean up merged lists of import or require statements. Remove duplicates introduced when combining files or refactoring modules.

Dictionary & Word Lists

Eliminate duplicate entries in word lists, dictionaries, or blocklists used by spell-checkers, autocomplete systems, or content filters.

Related Text Tools

Sort Lines

Find & Replace

Whitespace Cleaner

Word & Character Counter

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