Text Tools

Free Remove Duplicate Lines

Q: Should I keep the first or last occurrence?

Usually you keep the first occurrence because the original order is preserved. Keep-last is useful when the last version of a line has the most up-to-date information — for example in log files or versioned lists. Both options preserve the order of the kept lines relative to the rest of the file.

Q: Can it also sort and deduplicate?

Yes. Enable 'Sort A→Z' to sort the deduplicated lines alphabetically. This is useful for creating a canonical sorted list from an unsorted one. You can also reverse-sort with 'Sort Z→A'.

Clean up any list, CSV, email list or text file in one click. Removes repeated lines, keeps the unique ones — with case and whitespace options.

Instant Dedupe 100% Private Optional Sort Works on Mobile

Your Text

0 lines · 0 chars Live processing as you type

Ignore case Trim whitespace Remove empty lines Sort A→Z

Keep

Deduplicated Output

Input

Removed

Unique

0 lines · 0 chars

Tip: The output updates live as you type. Adjust the options above to fine-tune what counts as a "duplicate" — by default we ignore case and trim whitespace.

What Is a Duplicate Line Remover?

A duplicate line remover is a tool that scans text line by line and removes every repeated line, leaving only the unique lines. It's one of those tools you don't realise you need until you have 500 lines of email addresses with dozens of duplicates scattered throughout.

The tool is fast, private and completely free. It runs entirely in your browser — nothing is uploaded to any server.

How it works

The algorithm is simple and fast:

Split your text into lines (on every line break).
Normalise each line based on your options (lowercase for case-insensitive comparison, trim whitespace).
Track which lines have already been seen using a hash set — this makes the algorithm O(n) instead of the O(n²) you'd get with nested loops.
Keep the first (or last) occurrence of each unique line, in the order you specified.
Optionally sort the result alphabetically before output.

Example: before and after

Before (with duplicates)

apple banana apple cherry banana apple date

After (unique only)

apple banana cherry date

Options explained

Ignore case — when ON, "Apple", "apple" and "APPLE" count as the same line. When OFF, they are three distinct lines.
Trim whitespace — when ON, leading and trailing spaces are stripped before comparison, so " apple " and "apple" are the same line. When OFF, they are different.
Remove empty lines — when ON, blank lines are also removed from the output. Useful for cleaning up text that has random blank lines.
Sort A→Z — when ON, the deduplicated result is alphabetically sorted. Case-insensitive sorting uses locale-aware comparison, so "apple" comes before "Banana".
Keep first / last occurrence — controls which position a duplicate is kept in when multiple lines are identical. "First" preserves the original order (the most common choice). "Last" is useful when the last version of a line is the most current.

Common use cases

Email Lists

Deduplicate email lists before importing to your ESP or CRM.

CSV Data

Remove duplicate rows from CSV exports or database dumps.

Keyword Lists

Clean up keyword research lists to remove repeated terms.

Code Imports

Remove repeated import statements or log lines from output.

Product SKUs

Dedupe product codes or inventory lists before uploading.

Guest Lists

Remove duplicate names from event RSVP or mailing lists.

URL Lists

Clean up lists of URLs from sitemaps, crawls or backlink exports.

Log Files

Extract unique log entries or remove repeated error messages.

Why deduplicate?

Save time and space — a list of 5,000 entries with 40% duplicates is really only 3,000 unique entries. Deduplicating gives you an accurate count.
Improve data quality — duplicate emails mean duplicate sends. Duplicate SKUs mean inventory errors. Duplicate URLs waste crawl budget.
Prevent mistakes — accidentally processing the same record twice can cause billing errors, mailing list complaints or analytics confusion.
Cleaner analysis — when you know every entry is unique, counts, statistics and pivots are meaningful.

How does it compare to Unix uniq / sort -u?

Unix tools like sort -u and uniq do similar work but with different tradeoffs:

sort -u sorts first, then removes duplicates — so the output is always sorted.
uniq only removes adjacent duplicates — you need to sort first, and it doesn't have built-in case-insensitive or trim options.
This tool preserves your original order (by default), ignores case, trims whitespace, and gives you a keep-first or keep-last option — all without needing a terminal.

Privacy and security

This duplicate line remover runs entirely in your browser. Your text is never sent to any server, never stored anywhere, and disappears the moment you close the tab. Safe for confidential lists, private email addresses, unreleased data and any content you want to keep local.

Frequently Asked Questions

What is a duplicate line remover?

A duplicate line remover is a tool that scans text line by line and removes every repeated line, leaving only unique lines. It's used to clean up lists, CSV data, email lists, code output, search results and any text where repeated lines are unwanted.

How are duplicate lines defined?

A duplicate line is any line whose content is identical to another line, usually after optional whitespace trimming and case normalization. With "Ignore case" enabled, Hello and hello count as duplicates. With "Trim whitespace" enabled, Hello and Hello also count as duplicates.

Should I keep the first or last occurrence?

Usually you keep the first occurrence because the original order is preserved. Keep-last is useful when the last version of a line has the most up-to-date information — for example in log files or versioned lists. Both options preserve the order of the kept lines relative to the rest of the file.

Does it work with large files?

Yes. The tool runs entirely in your browser and can comfortably handle tens of thousands of lines. Files with hundreds of thousands of lines may take a few seconds but remain responsive because the algorithm runs in O(n) time using a hash set.

Does it preserve the order of lines?

Yes. Non-duplicate lines keep their original position. When duplicates are found, we keep the first occurrence (by default) and remove the later ones, so the final list reads top-to-bottom in the same order you originally wrote it.

Can it also sort and deduplicate?

Yes. Enable Sort A→Z to sort the deduplicated lines alphabetically. This is useful for creating a canonical sorted list from an unsorted one.

Will it remove empty lines?

Only if you enable the "Remove empty lines" option. By default, empty lines are treated as duplicates of each other and only one is kept. If you want a truly empty result without blank lines, turn that option ON.

Is this duplicate line remover free?

Yes. It is 100% free, requires no sign-up, and runs entirely in your browser. Your text never leaves your device.