A free email list cleaner with no upload

"Free" list cleaners usually mean you pay with the file. Uploading a customer or client list hands a third party a database of real people, often without a processing agreement — a problem under GDPR, under most NDAs, and under plain common sense.

A browser-only tool inverts that: the file is read with JavaScript in the tab, processed locally, and the export is generated on your device. No server sees the addresses.

What “no upload” technically means

The page reads the file with the browser's File API and parses it in memory. The only outbound requests are DNS lookups for domain names — gmail.com, not jane@gmail.com — which is public information anyway. Close the tab and the data is gone; nothing is stored server-side because there is no server.

What you can still verify

Duplicates, including Gmail dot and +tag aliases
Domain typos against provider names
Disposable and role addresses, by domain list
Whether each domain has a real mail server (MX)

What you cannot, and shouldn't be promised

Whether a specific mailbox exists, whether it is full, or whether the domain is a catch-all. Those need an SMTP conversation per address, which by definition means sending something to a server. Any tool claiming full inbox verification "without sending anything" is either guessing or lying about what it did.

When the free tier is enough

For a one-off cleanup of a small list, 100 addresses covers the typical spreadsheet. Beyond that, per-address pricing is where the hosted verifiers make sense — they charge roughly a cent per address or less at volume, and they do more per address than a domain check can.

ListSweep is free to 100 addresses and $19 once for unlimited use, which is aimed at the case hosted tools price badly: a few large cleanups a year, or an agency doing client lists every week.

Check your own list in about 30 seconds. Paste or drop a CSV — duplicates, typos, role addresses and dead domains, all handled in your browser. Free for the first 100 addresses, $19 once for unlimited.

Open the tool

Common questions

Can I use it on a client's list under NDA?

That's the case it was built for — the data never leaves the browser. Your NDA still governs what you do with the output, but no third-party processor is involved.

Does it work offline?

The page loads once, then parsing and dedupe work offline. MX checks need DNS, so they require a connection.

Last updated 2026-10-23.