Does removing duplicate lines preserve the original order?

Yes, the first occurrence of each unique line keeps its original position; only the later repeats are removed.

Are “Email@example.com” and “email@example.com” treated as duplicates?

That depends on whether case-insensitive matching is selected. By default, matching is exact and capitalization differences are treated as different lines.

Why might two identical-looking lines not be detected as duplicates?

A trailing space or other invisible whitespace difference can make two lines that look the same actually be different strings, which an exact match comparison will not flag as duplicates.

Remove Duplicate Lines

Paste your text below and instantly remove all repeated lines.

Input Text

Case-sensitive Trim whitespace

Keep:

How to Use

Paste or type your text into the input box — each line is treated as one item.
Choose your options: case-sensitive matching, whitespace trimming, and whether to keep the first or last duplicate.
Click Remove Duplicates to process the text.
Copy the cleaned output with the Copy Output button.

Case-sensitive means "Apple" and "apple" are treated as different lines. When off, they count as duplicates. Trim whitespace ignores leading and trailing spaces when comparing lines.

About this Duplicate Line Remover

Duplicate lines creep into lists from merged spreadsheet exports, copy-pasted data from multiple sources, or repeated entries in a keyword or email list. Finding them by eye in a list of any real size is slow and unreliable; a script-based comparison catches every repeat instantly.

Exact match vs. case-insensitive match

An exact match treats "[email protected]" and "[email protected]" as different lines, since capitalization differs. A case-insensitive match treats them as duplicates. Which mode to use depends on the data: email addresses and usernames are often case-insensitive in practice, while code identifiers or exact quotes usually need exact matching to preserve meaning.

Whitespace and trailing spaces

Two lines that look identical can still fail to match if one has a trailing space or extra whitespace the eye doesn't catch. This is a common reason a manual "looks the same" check misses duplicates that an automated comparison correctly identifies as different (or the reverse: fails to flag as duplicate) lines.

Common uses

Cleaning a merged mailing list before an email send, to avoid contacting the same address twice
Deduplicating a keyword list before importing it into an ad platform or SEO tool
Cleaning up a combined export from multiple spreadsheets or CRM systems
Removing repeated lines accidentally introduced by a copy-paste error