About this tool

Compare Two Lists is a small, single-purpose web tool. It does one thing well: take two lists and show you which items are only in the first, only in the second, or in both. There is no sign-up, no upload and no tracking of the content you paste — the comparison runs entirely in your browser using JavaScript, so your data never leaves your device.

It was built by Marcio, who makes lightweight, focused tools for everyday data chores: the kind of quick job that should not require installing software, creating an account or trusting a stranger with a confidential list. If a task can be done safely and instantly in the browser, that is the goal here.

The tool is designed to be honest about what it does. It treats each list as a set of unique items and ignores order, which is the right model for comparing records like emails, IDs and product codes. If you need an order-sensitive, line-by-line comparison instead, the article on set difference vs. text diff explains the distinction and points you to the right kind of tool.

Questions, corrections or ideas for improvement are welcome — see the contact page.