Removing duplicate lines from a list

Deduplicating a list of lines is one of those tasks that is trivial in principle and annoying in practice, because two lines that look identical often are not. A trailing space, a different capitalisation, or a stray tab makes them distinct as far as any tool is concerned.

So the useful options are case sensitivity and trim whitespace. With whitespace trimming on and case sensitivity off, "user@example.com " and "User@Example.com" correctly collapse into one entry. Without them, you keep both and wonder why. The tool is in the ToolHub text section.

Remove Duplicate Lines: the facts that matter

How to do it, step by step

1. 1Open the duplicate line remover in ToolHub and paste your list.
2. 2Turn on whitespace trimming. This alone catches most missed duplicates.
3. 3Turn off case sensitivity for emails, URLs and names, where case does not signify.
4. 4Keep case sensitivity on for anything where case matters, like codes, hashes or identifiers.
5. 5Compare the before and after line counts to confirm it did what you expected.

Three things worth knowing

• Whitespace trimming on, case sensitivity off, is the right default for contact lists.
• Check the line count before and after. A suspiciously large drop usually means case sensitivity was off when it should not have been.
• For anything larger than a few thousand lines, this belongs in a script rather than a browser tool. CodeAiMan's web development team builds that kind of data cleanup into the app itself.

Common problems, solved

Where to run it

This tool is part of the ToolHub tool library, a library of over 1,000 browser-based tools covering PDF, image, video, audio, text and developer work. Everything runs in the browser and none of it needs an account.

ToolHub is built by codaiman.com, an AI-first software company in Ahmedabad. Related to this page: Web development custom websites and web apps in react, next.js and typescript, including pwas and api work.

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