How HandleProbe decides

Most sites keep profiles at a predictable address, like github.com/name or t.me/name. HandleProbe requests all of those addresses in parallel, fifty at a time, so a full search finishes in a minute or two.

A page loading proves very little. Plenty of sites answer every address with a page, whether the account exists or not, and some answer automated visitors with a bot check instead.

Each page is reduced to about 30 signals: the HTTP status, whether the username appears in the title or the page’s structured data, profile and error wording, the shape of the page, and how it compares with pages seen before. A small trained model and a set of hand-tuned rules both score those signals, and the blend becomes one of four answers.

• FoundThe page reads as a real profile and survived the second check.
• UnconfirmedSomething profile-like, but not enough to say. Common, and usually noise.
• Not foundThe site said the account doesn't exist, or the page reads as an error.
• No responseNo usable answer: a timeout, a block, or a broken page.

A Found is a claim that an account exists, so it has to survive three more tests first.

• An HTTP 404 or 410 always means Not found. Any other error code is Unconfirmed at most.
• A bot check or an error page is Unconfirmed at most.
• The site is also asked for a username that can’t exist. If it answers with the same page, the result drops to Unconfirmed, because the page says nothing about this account.

These figures come from the Aliens Eye project, measured on 135 sites its model never saw during training.

of usernames that don't exist were wrongly reported as Found.

1%

of usernames that don't exist were wrongly reported as Found.

of real accounts were reported as Found. The rest came back Unconfirmed or missed.

49%

of real accounts were reported as Found. The rest came back Unconfirmed or missed.

precision: when it says Found, it's right about 96 times in 100.

0.96

precision: when it says Found, it's right about 96 times in 100.

In short, a Found is usually right, but about half of real accounts don’t show up as Found. The detector is tuned to give you fewer false leads rather than to catch everything.

Treat every result as a lead to check, not a fact. A Found means an account with that username exists. It doesn’t mean it belongs to the person you have in mind.

• It only reads public profile pages. It doesn’t log in, use site APIs, or see anything private.
• It doesn’t try spelling variations of the username.
• It doesn’t keep your searches. See Privacy and acceptable use.

The detection, the site catalogue and the trained model are Aliens Eye, an open-source username scanner by Aaron Thomas, released under the MIT license. HandleProbe is an independent website built on top of it.