Remove duplicatesfrom any list.

No. Everything runs in JavaScript inside this tab — you can confirm it by opening your browser's network tab and clicking the button, where you'll see no request go out. This tool is client-side by design rather than by convenience, because de-duplication is exactly where people paste customer lists, email addresses and invoice numbers.

Line breaks, commas, semicolons, tabs and pipes — and any mix of them in the same list. You don't select one; each is used only if it's actually present in what you pasted. The summary tells you which ones were applied, so you can always see how your list was split.

The first. In practice the earlier entry is the original and the later ones are the accidental repeats, and keeping the first also preserves the order you pasted. If you'd rather have it alphabetical, use the Order dropdown — that sorts the result without changing which copy was kept.

With it off, Apple and apple are two different items. With it on, they merge and the first spelling you pasted is the one kept. Because that can merge things you meant to keep apart, the "What was removed" panel lists every form that collapsed together, so the decision is visible rather than silent.

Yes. Text wrapped in single or double quotes is treated as one item, so "Smith, John" survives intact and the quotes are stripped from the output. If you need the quotes back, pick the Quoted CSV output format.

Comfortably into the hundreds of thousands of items. Matching uses a hash lookup rather than comparing every item against every other one, so doubling the list roughly doubles the time instead of quadrupling it. The practical limit is your browser's paste size, not the de-duplication.

Yes — drop a .txt, .csv, .tsv or Excel file (.xlsx, .xls) anywhere on the input box, or use Choose file. Nothing is uploaded: your browser reads the file locally, including spreadsheets. Excel files with more than one sheet use the first sheet, and you'll be told which one.

It keeps your table intact and gives you a tick box per column. The ticked columns decide what counts as a duplicate, and whole rows are kept or removed together — exactly like Excel's own Remove Duplicates. Every column starts ticked, which only removes rows identical the whole way across. Untick down to a single column when you want, say, one row per email address.

Email ignores case, +tags, and dots inside Gmail addresses. Web address ignores http/https, www., trailing slashes, #fragments and tracking parameters like utm_source. Phone number compares digits only and ignores the country code. Loose text ignores case, punctuation and repeated spacing. Each rule is kept narrow on purpose — the Gmail dot rule, for instance, is applied only to Gmail, because on a company domain j.smith@ and jsmith@ can be two different people.

Only if you use one. The spreadsheet reader is a few hundred kilobytes, so it isn't downloaded when the page loads — it's fetched the first time you actually pick an .xlsx file. If you paste text, you never download it at all.