--- title: Free IP Address Lookup description: Look up any IPv4 or IPv6 address — the network it belongs to (ASN and operator), the announced BGP prefix, the registry country and its reverse DNS name. Identify the owner of an address in your logs, check a mail server's PTR, and jump straight into a ping, traceroute or blocklist check on the same IP. canonical: https://watchfor.io/ip-lookup --- [Back to all free tools](/free-tools) # IP Address Lookup Look up any IPv4 or IPv6 address — the network it belongs to (ASN and operator), the announced BGP prefix, the registry country and its reverse DNS name. Identify the owner of an address in your logs, check a mail server's PTR, and jump straight into a ping, traceroute or blocklist check on the same IP. Result No result yet Enter the inputs above and press Run. Results appear here in a moment. Monitor this 24/7 — get alerts on the first failure. [Start free](/auth/sign-up) Only run these tools against systems you own or are authorized to test. Using them to scan or probe systems without permission violates our [Terms](/legal/terms). ## What is IP Address Lookup ? An IP address on its own tells you nothing — 185.199.108.153 could be a home router, a scraper, a CDN edge or your own server. What you want to know is who announces it: the autonomous system (ASN) and the organisation behind it, the BGP prefix it belongs to, the registry region, and what it's called in reverse DNS. That's enough to tell GitHub Pages from a residential ISP, a Tor exit from a search engine crawler, and your cloud provider's range from an address that shouldn't be talking to you at all. This tool looks up any IPv4 or IPv6 address and returns exactly that: ASN and network name from the global routing table, the announced prefix, the registry country, and the PTR record. It deliberately does not guess a city from a commercial database — the registry country is where the block was allocated, and the tool says so. From the result you can jump straight into a ping, traceroute, port check or blocklist check on the same address. ## How it works Two lookups, both against public data, no database to go stale: - 1 Origin ASN from the routing table — Team Cymru's IP-to-ASN service answers a DNS TXT query with the ASN, the prefix and the registry that allocated it — derived from live BGP data. A second query turns the ASN into its registered name. - 2 Reverse DNS — A PTR query for the address, the same one mail servers make. No PTR is a normal answer for many addresses and a finding for a mail host. - 3 Nothing else — No connection to the address, no port scan, no geolocation guess. The result is what the internet publicly says about the address. For your own address, What Is My IP shows the same fields plus the approximate location your connection reveals. ## When you'd use it ### An address in the logs Failed logins, a burst of requests, an unfamiliar SSH client. The ASN and name say whether it's a cloud provider (probably a bot on a rented VM), a residential ISP (a person, or a compromised machine) or a known scanner network. ### Verifying a crawler or webhook source Googlebot comes from Google's ASN with a PTR ending in googlebot.com ; Stripe's webhooks come from published ranges. An address claiming to be either from an unrelated network is something else. ### Mail server checks Before trusting or sending from an address, see its PTR and network. Then run the SMTP test against the host for banner, TLS and relay behaviour. ### Allow-listing and firewall rules The BGP prefix is the block to allow-list when a partner gives you one address and their traffic arrives from its neighbours. ## Reading the result ### ASN and network name AS16509 Amazon.com means the address is in AWS's routed space — the customer behind it could be anyone. AS15169 Google with a Googlebot PTR is Google. The name is the registry's, cleaned of handles. ### BGP prefix The block currently announced that contains the address, e.g. 185.199.108.0/22 . Useful as an allow-list unit and as a sign of how big the operator is. ### Registry country Where the block was allocated by ARIN, RIPE, APNIC, LACNIC or AFRINIC. It is not the host's location: a RIPE-allocated block can serve traffic from Singapore. ### Not announced No ASN found means the address isn't in the global routing table — reserved space, a bogon, an unallocated block, or a range withdrawn since. Traffic from such an address is spoofed or misconfigured. ## Check it yourself dig +short TXT 153.108.199.185.origin.asn.cymru.com The address is reversed octet by octet. The answer is ASN | prefix | country | registry | allocated . ## Common pitfalls ### Reading the country as the location It's the allocation region. For a location estimate you need a geolocation database, which is a guess with its own error rate; this tool doesn't pretend to have one. ### Treating a cloud ASN as the culprit Reporting AS16509 to abuse@amazon reaches the provider, not the tenant. Include timestamps and the exact address; the provider maps it to a customer. ### Private and CGNAT addresses 10.x , 192.168.x , 100.64.x and friends aren't routed on the internet and are rejected by the tool — they identify nothing outside your own network. ## Run IP Address Lookup on every change, not just once. Get alerts the moment something breaks — across HTTP, DNS, SSL, RDAP, ping, blacklist and more. Free forever for 10 monitors. No card. [Start free](/auth/sign-up) ## Frequently asked questions What is an ASN? An Autonomous System Number identifies a network that routes its own address space on the internet — an ISP, a cloud provider, a large company. Every routed IP belongs to exactly one AS at any moment, which is what makes the ASN the most reliable way to say whose address it is. Can I find the exact location of an IP address? Not reliably, and not from public data. Geolocation databases estimate a city from allocation records, latency measurements and user contributions, and are routinely wrong by hundreds of kilometres. The registry country here is the allocation, stated as such. Why does my address show a different owner than my ISP? Your ISP may lease address space from a larger operator, or route through a parent carrier's ASN. The registry's name for the block is what's shown. Does the lookup contact the IP address? No. Both queries go to DNS servers that publish routing and reverse-DNS data. The address itself never sees a packet from this tool — use ping or the port checker for that. Does it work for IPv6? Yes — the same ASN lookup exists for IPv6 ( origin6.asn.cymru.com ) and PTR lookups work under ip6.arpa . ## Related network tools - [PingICMP echo request — round-trip time, jitter, packet loss.](/ping-test) - [TracerouteTrace the network path hop by hop with per-hop latency (MTR-style).](/traceroute-online) - [Port CheckerTest TCP port reachability and optionally grab the server banner.](/port-checker) - [Blacklist CheckTest an IP or domain against 15+ DNS-based blocklists (RBLs).](/blacklist-checker) --- Canonical page: https://watchfor.io/ip-lookup · Site guide: https://watchfor.io/llms.txt