10 Best Reverse IP Lookup Tools for Founders [2026 Updated]

1. DomainTools

• Type: Paid
• URL: https://www.domaintools.com
• Overview: DomainTools provides a commercial Reverse IP product and API that returns domains sharing the same IP address, built from a large historical DNS dataset. It’s designed for marketing and investigative use cases such as competitor discovery, account-based prospecting, and brand protection.

2. WhoisXML API Reverse IP

• Type: Paid
• URL: https://whoisxmlapi.com/reverse-ip-lookup.php
• Overview: WhoisXML API offers Reverse IP Lookup via a web lookup, API, and bulk DNS database downloads to find domains tied to an IP address and historical first-seen/last-updated timestamps. The product is built for scalable integration into lead enrichment, digital footprinting, and DNS asset discovery workflows.

3. SecurityTrails

• Type: Paid
• URL: https://securitytrails.com
• Overview: SecurityTrails provides comprehensive DNS and reverse-IP search capabilities through its platform and API, returning current and historical domains hosted on an IP or ASN. Marketers use it for competitor research, infrastructure mapping, and identifying related web properties for outreach.

4. Host.io

• Type: Paid
• URL: https://host.io
• Overview: Host.io offers a reverse-IP endpoint and web queries that list domains sharing an IP plus related DNS, backlink and technology signals. It’s aimed at enrichment use cases—discovering co-hosted sites, potential partners, and prospect lists based on hosting relationships.

5. Shodan

• Type: Paid
• URL: https://www.shodan.io
• Overview: Shodan is an internet-connected device search engine with the ability to enumerate hosts and associated domains for IP addresses, using its indexed banner and certificate data. Marketers and researchers can use Shodan’s IP-to-host insights to discover adjacent web properties and hosting infrastructure.

6. Censys

• Type: Free
• URL: https://censys.io
• Overview: Censys indexes internet-exposed hosts and certificates and allows reverse lookups from IPs to observed domain names and TLS certificates via web interface and API. It’s useful for marketing intelligence that needs verifiable host/domain pairings and historical certificate-based relationships.

7. ViewDNS.info

• Type: Free
• URL: https://viewdns.info/reverseip/
• Overview: ViewDNS.info provides a simple free Reverse IP Lookup web tool that lists domains hosted on the same IP address using aggregated DNS records. It’s a quick, no-signup option for marketers to spot co-hosted domains or potential content partners.

8. SpyOnWeb

• Type: Free
• URL: https://www.spyonweb.com
• Overview: SpyOnWeb aggregates signals (IP addresses, Google Analytics IDs, AdSense IDs, name servers) to link websites and show domains that share the same hosting or tracking identifiers. Marketers use it for competitive analysis, discovering networks of sites owned by the same organization, and finding outreach targets.

9. IPinfo

• Type: Paid
• URL: https://ipinfo.io
• Overview: IPinfo provides IP intelligence including reverse-IP/hostname lookups and enriched ASN/owner metadata via API and bulk datasets. It’s commonly used in marketing workflows to map company-owned infrastructure, enrich prospect records, and segment accounts by hosting footprint.

10. HackerTarget Reverse IP Lookup

• Type: Free
• URL: https://hackertarget.com/reverse-ip-lookup/
• Overview: HackerTarget offers a free web reverse-IP tool and a simple API that searches aggregated DNS corpuses to list domains resolving to an IP or CIDR block. It’s a lightweight option for marketers to quickly enumerate co-hosted domains for discovery and initial prospecting.