What is Reverse IP Lookup?
Definition: A technology that identifies which companies are visiting your website by matching visitor IP addresses to known corporate IP ranges, revealing anonymous traffic as named accounts.
Most website visitors leave without filling out a form. Reverse IP lookup unmasks some of them by matching their IP address against databases of corporate IP ranges. When someone from Microsoft's office network visits your pricing page, the tool says "Microsoft visited your pricing page." You don't get the individual's name, but you get the company.
6sense, Clearbit Reveal, and Leadfeeder are the main tools in this space. 6sense matches IPs at the account level and layers on intent data. Clearbit Reveal identifies companies and enriches with firmographic data. Leadfeeder focuses specifically on website visitor identification.
The practical value for GTM Engineers: turn anonymous web traffic into outbound targets. If a company visits your pricing page twice in a week, that's a strong buying signal. You look up decision-makers at that company via Apollo or Clay, and send a targeted cold email referencing the problem your pricing page addresses (without mentioning you know they visited).
Limitations are real. Remote work broke this partially because home IP addresses don't map to companies. VPNs mask corporate IPs. Small companies rarely have static IP ranges. Match rates typically run 15-30% of total traffic. It's a useful signal source, not a comprehensive visitor identification solution. Combine it with other intent signals for the fullest picture.