Duplicate Line Remover
Removes duplicate lines from a pasted list and shows how many it found.
What this tool does
Paste a list of lines — emails, phone numbers, IDs, log lines, any text where each line is one item — and the tool removes the repeated ones, keeping only the first occurrence of each. The result is ready to copy, along with a summary of how many lines there were in total, how many were unique, and how many duplicates were removed.
How the tool decides two lines are the same
Two options control the comparison, both on by default: "Case-sensitive comparison" off treats "Test@Test.com" and "test@test.com" as the same line — the most common case when cleaning up an email list or general data. Turn it on when you need literal exactness, such as comparing log lines where case can matter. "Trim leading/trailing whitespace" on treats "abc" and "abc " (with trailing space) as the same line — leftover whitespace from copy-pasting is usually noise, not information. Both options only decide WHICH lines count as duplicates — the text shown in the result is never altered (not lowercased, not trimmed), always exactly as it appeared on its first occurrence.
How empty lines are handled
An empty line has no special rule — it's compared exactly like any other line: the first one survives, the rest count as duplicates. That's why pasting text that ends with a line break (common when copying from a text editor) produces one extra empty line at the end of the result — that's not a bug, it's the same mechanical rule being applied consistently.
Result order: original or alphabetical
"Preserve original order" on (default) keeps lines in the order they first appeared in the pasted text — the most intuitive behavior in most cases. Turned off, the result comes out sorted alphabetically, which makes it easier to scan a large list once it's clean (for example, to find a specific email). Neither mode changes which line survives — only the display ORDER is affected, never which text represents each unique line.
Known limitations
Comparison is always whole line against whole line — the tool doesn't detect partial duplicates (two lines that are similar but not identical under the chosen rules), nor does it ignore whitespace differences in the MIDDLE of a line (only at the edges, and only when "Trim" is on). There's also no fuzzy/approximate matching mode — two lines only count as duplicates when they're exactly equal under the comparison rules chosen.
Frequently asked questions
By default, comparison ignores case — the most common case when cleaning up an email list or general data. Turn on "Case-sensitive comparison" to treat them as different lines.
Turn on "Case-sensitive comparison" and turn off "Trim leading/trailing whitespace" — with both set that way, only byte-for-byte identical lines count as duplicates.
The pasted text likely ends with a line break (very common when copying from an editor) — that creates an extra empty line at the end, treated like any other line (see "How empty lines are handled", above). It's not a processing error.
Always the first occurrence, at the position it appeared in the original text — even with "Preserve original order" off (in that case only the DISPLAY order changes to alphabetical, the chosen line is still the first one).
The same sensitivity used to decide duplicates is used for sorting — with the option on, uppercase and lowercase are compared by exact value (e.g. "Apple" before "banana"); off, sorting ignores case (e.g. "apple" and "Apple" end up next to each other, regardless of which came first).
Because a line that never repeated has no duplicate to show — that list exists specifically to answer "which lines specifically repeated, and how many times". Everything else in the result (including unique lines) is already in the "Result without duplicates" field, above.
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