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🗃️ Deduplicate

Remove Duplicate Lines Online

Paste any list and instantly remove all repeated lines. Keeps the first occurrence. Free, browser-only, no account required.

🗃️ Remove Duplicates →

Common use cases for removing duplicate lines

  • 🔑 Keywords lists — remove duplicate keywords from SEO lists or ad groups
  • 📧 Email lists — deduplicate mailing list exports
  • 🗂️ Data cleaning — remove repeated entries from CSV exports
  • 💻 Code logs — clean repeated log messages
  • 📋 To-do lists — remove accidentally duplicated tasks
  • 🌐 URL lists — deduplicate link collections
How it works

Text is split on newlines. Each line is trimmed and compared case-sensitively using a JavaScript Set. The first occurrence of each unique line is kept; all subsequent duplicates are discarded. The result is output in original order.

🗃️ Deduplicate Lines →

Frequently Asked Questions

Yes, by default. 'Hello' and 'hello' are treated as different lines. To do case-insensitive deduplication, first convert all text to lowercase, then remove duplicates.
Multiple consecutive blank lines are reduced to one. If you want to remove all blank lines entirely, use the 'Remove Empty Lines' option in the same toolkit.
No hard limit. The tool uses a JavaScript Set for O(n) performance — 100,000+ line lists process in milliseconds on a modern device.
Yes. The first occurrence of each line is kept in its original position. Only subsequent duplicate occurrences are removed, so the sequence of unique lines is unchanged.
You can run Remove Duplicates first, then click Sort Lines (A–Z) to alphabetize the result. Both operations are available in the Text Formatter Toolkit.
The deduplicator works on full lines. For CSVs, if each row is on its own line, duplicate rows will be removed correctly. It does not deduplicate individual values within a line.

How deduplication works

1
Split on newlines — Text is broken into an array of individual lines.
2
Hash into a Set — Each trimmed line is added to a JavaScript Set. Sets only hold unique values, automatically discarding repeats.
3
Reconstruct output — Unique lines are joined back with newlines in their original first-seen order.
4
Report savings — The tool displays how many duplicate lines were removed and what percentage of the list was deduplicated.

Remove Duplicate Lines – Clean Lists and Deduplicate Text Instantly

Removing duplicate lines is a common data cleaning task in development, content work, and data analysis. When you merge two keyword lists, combine CSV exports, or aggregate data from multiple sources, duplicate entries are almost inevitable. Manually spotting and deleting duplicates from a 1,000-line list is impractical — this tool does it instantly with a single click.

Common use cases include deduplicating keyword lists for SEO campaigns, cleaning email subscriber lists, removing repeated log entries, merging lists of product IDs or SKUs, and normalizing text data before import. The tool preserves the original order while removing exact duplicates. Optionally sort alphabetically after deduplication for further processing. All processing is done locally in your browser — your data never leaves the page.

  • Case sensitivity — "Apple" and "apple" can be treated as duplicates or distinct depending on your use case
  • Empty lines — Option to also remove blank lines as part of the cleanup
  • Performance — Handles lists of tens of thousands of lines without issue

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