Remove Duplicate Lines

Remove duplicate lines from text with case-insensitive, trim, and sort options.

Free Tool

How to use Remove Duplicate Lines

Our Remove Duplicate Lines tool cleans lists and text blocks by removing repeated entries — with granular control over case sensitivity, which occurrence to keep, and how to sort the output. Paste your text into the input area. The tool works on any line-separated text: email lists, keyword lists, URL lists, product names, code imports, data exports, or any other list format. Configure the deduplication options: • Case Sensitivity — "Case Sensitive" treats "Apple" and "apple" as different entries and keeps both. "Case Insensitive" treats them as the same and removes one. For email and URL deduplication, use case insensitive — domains are case-insensitive by standard. • Trim Whitespace — removes leading and trailing spaces from each line before comparison. Highly recommended — a space difference like " apple" vs "apple" causes false uniqueness. Keep this enabled unless your data intentionally uses whitespace. • Keep First or Last Occurrence — when a duplicate is found, which copy should survive? "First" preserves the original order of first appearances (most common). "Last" updates to the most recent occurrence — useful when your list has corrections appended at the bottom. • Remove Empty Lines — strips blank lines from the output, producing a clean compact list. • Sort Output — rearranges results alphabetically (ascending or descending) or by line length. Sort alphabetically for organized reference lists; sort by length for formatting analysis. Results show your deduplicated text with a summary: original line count, unique lines kept, duplicates removed, and percentage reduction. A "Removed Lines" panel lists every duplicate that was removed — copy it to review what was eliminated. Copy the cleaned output in one click or paste directly into your target application. Ideal for data cleaning, keyword list preparation, email list hygiene, and removing repeated lines from code files.

Frequently Asked Questions

What is the difference between case-sensitive and case-insensitive deduplication?

Case-sensitive treats "Hello" and "hello" as different — both are kept. Case-insensitive treats them as identical — one is removed. For email addresses and URLs (which are case-insensitive by standard), always use case-insensitive mode. For code and passwords where case matters, use case-sensitive.

What does trimming whitespace do?

Trimming removes leading spaces (before the text) and trailing spaces (after the text) from each line before comparing. Without trimming, "apple" and " apple" (with a leading space) are treated as different entries. Since invisible spaces are a common cause of false duplicates in exported data, trimming is recommended in most cases.

Can I see which lines were removed?

Yes. The "Show Removed Lines" toggle reveals a panel listing every duplicate that was eliminated. You can copy these removed lines separately — useful for auditing what was cleaned, or if you need to verify the deduplication result is correct before discarding them.

What is the maximum number of lines this tool can handle?

The tool processes text entirely in your browser with no server upload, so practical limits depend on your device's memory. For most use cases (up to 100,000 lines), it processes instantly. Very large files (millions of lines) may be slow — for those volumes, use a command-line tool like sort -u on Unix/Mac.

How do I remove duplicate lines while keeping the original sort order?

Use "Keep First Occurrence" without enabling "Sort Output." This preserves the original order of first appearances exactly. The first time a line appears in the input, it's kept in its original position. All subsequent identical lines (duplicates) are removed. The output order matches the input order of unique lines.

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