Free tool
Find the company behind an IP address
Enter a public IP address and see which organization owns that network — company name and domain. This is the same lookup PageFox runs on your website traffic to show you which companies are visiting, even when nobody fills out a form.
Company-level only: this resolves the network owner behind a public IP. It never identifies a person. The address is looked up, not stored.
What a reverse IP lookup is
A normal DNS lookup turns a domain name into an IP address. A reverse IP lookup runs the question backwards: you start from an IP address and find out which organisation is responsible for that block of addresses. Every visit to a website arrives from an IP, and every public IP belongs to a registered network owner, so the answer always exists — the only question is whether the owner is a company or a provider.
When the owner is a company network — an office, a corporate VPN, a campus — naming it tells you which business was on your site. That single fact is the whole basis of B2B visitor identification: no form, no cookie consent banner to click through, no login, just the network the request came from. When the owner is a consumer ISP, a mobile carrier or a commercial VPN, the lookup names the provider instead, and the honest conclusion is that you do not know who the visitor was.
The tool above tells you which of those two cases you hit, and says so in plain words rather than dressing an ISP up as a match.
Where the data comes from, and where it stops
The lookup calls the same commercial IP-intelligence provider PageFox uses in production, and then applies the product's own rule about what counts as a match. Only company-grade networks are reported as a company. Everything else — ISP, residential, mobile, VPN or proxy, hosting, anycast, satellite — resolves to a provider and is returned as unmatched, with the network owner named so you can see why.
The limits are worth stating before you build anything on this:
- Home and mobile visitors do not resolve. Someone reading your pricing page on a phone, on hotel Wi-Fi, or from a home broadband line resolves to the carrier or ISP — never to their employer.
- VPNs and privacy proxies break the link on purpose. That is what people install them to do, and no IP-based product can undo it.
- A match is a company, not a person. An IP identifies a network, so the strongest honest claim is “someone at this company was here”. PageFox only learns who, specifically, when a visitor tells its assistant.
- Most websites will not resolve most of their traffic. A large share of real visits come from consumer networks, so expect a meaningful result on the business portion of your traffic and nothing at all on the rest. PageFox publishes no headline identification figure for this reason: the only number that means anything is the one measured on your own site.
- Private and reserved ranges can never match. Addresses such as 10.x.x.x or 192.168.x.x are internal to a network and are rejected by the tool rather than guessed at.
None of that makes the signal weak. It makes it narrow and honest, which is the version you can act on. The longer background — how the whole category works, and what it costs — is in our guide to website visitor identification software.
IP to company API
A one-off lookup answers a question. An IP to company API answers it continuously, for every visit, and puts the result where your team already works. PageFox does the resolution on live traffic as it happens, then exposes the identified companies — with the pages they read, their visit history and their intent score — through the read-only REST API on the Business plan.
The call is a standard authenticated GET. Ask for the companies identified on one website:
curl --fail-with-body \
--header "Authorization: Bearer $PAGEFOX_API_KEY" \
"https://pagefox.co/api/v1/companies?website_id=00000000-0000-4000-8000-000000000000&page=1"A successful response is JSON with data and pagination. One identified company row looks like this:
{
"data": [
{
"kind": "company",
"id": "company_example_1",
"name": "Northwind Example",
"domain": "northwind.example",
"industry": "Software",
"employee_count": 84,
"location": "Toronto, CA",
"relationship_status": "new",
"source": "pdl",
"match_confidence": "high",
"linkedin_url": null,
"first_seen_at": "2026-08-20T09:30:00.000Z",
"last_seen_at": "2026-08-21T11:15:00.000Z",
"sessions_count": 3,
"pages_viewed_total": 8,
"max_lead_score": 88,
"leads_count": 1,
"conversations_count": 1,
"locked": false,
"person": null,
"last_session_source": {
"source": "google",
"referrer": "https://www.google.com/",
"utm_params": null,
"geo": {
"city": "Toronto",
"country": "CA"
}
}
}
]
}Note locked: when a workspace passes its plan's company-metering limit, the row stays visible but its identity fields are deliberately redacted, and your integration should keep the row as locked rather than overwrite richer CRM data with nulls. The full contract — every route, scope, page size and error shape — is in the PageFox API reference, and the canonical wire definition is the public OpenAPI document linked from it.
From one lookup to every visit
Checking a single IP by hand is useful when you already have an address and want to know who owns it. It does not help with the visitors you never knew about — and those are the ones worth having. On your own site, PageFox runs this lookup continuously: company-network visits are matched, logged with pages viewed and time on site, scored for buying intent, and routed to email or Slack, so you see which companies researched you and what they cared about. Its AI assistant then engages the visitor while they are still on the page, which is how the visits that IP lookup cannot resolve turn into named leads anyway.
Plans, limits and prices are published on the PageFox pricing page; the free plan is enough to see real identified companies on your own traffic. Start Free to see the companies already visiting your site.
Reverse IP lookup FAQ
- What is a reverse IP lookup?
- A normal DNS lookup turns a domain name into an IP address. A reverse IP lookup goes the other way: you start with an IP address and find out who is responsible for that block of addresses. For B2B websites the useful answer is the organisation that owns the network — which, when someone is browsing from an office or a corporate VPN, is the company they work for.
- What is an IP to company API?
- It is the same lookup exposed as a programmable endpoint rather than a form, so your own software can ask the question. PageFox does this continuously on live website traffic and exposes the resolved companies through its REST API on the Business plan, so you can sync identified companies into a CRM or warehouse instead of copying them by hand.
- Why did my IP address not return a company?
- Because not every IP belongs to a company. Residential broadband, mobile data, most VPN exits, hosting providers and anycast networks resolve to the provider that owns the range, not to the visitor’s employer. PageFox deliberately reports those as an unmatched network and names the provider, rather than presenting an ISP as though it were the company visiting your site.
- How reliable is IP to company identification?
- Reliable when it resolves, and honest when it does not. A company-grade network is a strong signal; a consumer or mobile network is no signal at all. That is why a large share of any real website’s visitors will never resolve to a company, and why PageFox publishes no headline identification figure — it depends entirely on your traffic mix, and your own dashboard shows the real number for your site.
- Is a reverse IP lookup personal data?
- This tool answers a question about a network, not about a person: it returns the organisation that owns an IP range and never a name, an email address or a profile. PageFox identifies visiting companies at company level and captures person-level details only when a visitor chooses to give them in conversation. Nothing you type into the tool above is stored.