1. Company lookup from the IP address
Tools like Leadfeeder, Snitcher and Albacross match a visitor's IP address to the company that owns it. It works for visitors on an office network of a mid-size or large company.
It works less well for small businesses' audiences: people browsing from home, on mobile data, or working for a company of five. Those IP addresses belong to an internet provider, not to the company you'd want to know.
2. Person-level identity resolution
Some tools go further and match visitors to a named person, using cookies and data bought from publisher networks. RB2B, for example, says on its own site that its person-level identification is US-only.
In the EU and UK this kind of matching needs a legal basis most small businesses can't show, so these tools either don't offer it there or ask you to collect consent first.
3. Letting visitors identify themselves
The visitors worth knowing usually want something from you: a quote, a call, a price, an answer. If you offer that at the right moment, they tell you who they are, and they expect to hear from you.
That's the approach Signal takes. It doesn't look anyone up. It reads what a visitor does, works out what they need and how soon, and offers the next step. When they book a call or ask for a call back, you get their name, how to reach them, and the whole visit.
Which should you use?
If you sell to large companies and need account lists, an IP-lookup tool is useful. If you're a small business, an agency or a trade, most of your ready visitors are people, not accounts, and they'll talk to you if you make it easy.