ASN Lookup

Look up Autonomous System Number details for any IP address or ASN. View owner, country, IP ranges, and network routing information.

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APIPOST /api/v1/network/asn
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Try also: IP Geolocation
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Key Features

100% Free

No registration required, unlimited checks

Instant Results

Real-time analysis with detailed output

REST API Access

Integrate into your workflow via API

Accurate Data

Live queries to authoritative sources

What is ASN Lookup?

The ASN lookup retrieves detailed information about any Autonomous System Number or finds the ASN responsible for a given IP address. Results include the organization name, country of registration, RIR (Regional Internet Registry), allocated IP prefix ranges, total IP address count, and BGP routing data. An ASN identifies a network — such as an ISP, cloud provider, corporation, or university — that controls a block of IP addresses and manages its own routing policy on the internet.

This free ASN lookup tool is used by network engineers analyzing peering and routing relationships, security researchers tracing IP addresses back to their controlling organization, compliance teams verifying which entity manages specific network blocks, and anyone investigating the ownership and infrastructure behind an IP address. The tool accepts both ASN numbers (e.g., AS15169 for Google) and IP addresses, making it flexible for different investigation starting points.

How to Use

  1. 1Enter an ASN number (e.g., AS15169) or any IP address to find its associated ASN
  2. 2Click 'Run Check' to query ASN databases and BGP routing tables
  3. 3Review the organization name, country, and RIR (ARIN, RIPE, APNIC, LACNIC, or AFRINIC)
  4. 4Examine the list of allocated IP prefix ranges to understand the network's size and scope
  5. 5Use the information for network analysis, security investigation, or peering research

Who Uses This

System Administrators

Monitor and troubleshoot infrastructure

Developers

Debug network issues and integrate via API

SEO Specialists

Verify domain configuration and performance

Security Analysts

Audit and assess network security

Frequently Asked Questions

What is an ASN (Autonomous System Number)?
An ASN is a globally unique number assigned to a network — called an Autonomous System — that controls a block of IP addresses and has its own routing policy. Every organization that connects directly to the internet backbone (ISPs, cloud providers, large corporations, universities) has one or more ASNs. For example, Google operates AS15169, Cloudflare operates AS13335, and Amazon AWS uses multiple ASNs. ASNs are essential for BGP (Border Gateway Protocol) routing, which determines how traffic flows between networks on the internet. ASNs are assigned by Regional Internet Registries: ARIN (North America), RIPE (Europe/Middle East), APNIC (Asia-Pacific), LACNIC (Latin America), and AFRINIC (Africa).
How do I find the ASN for an IP address?
Enter the IP address in the ASN Lookup tool and click Run Check. The tool queries BGP routing tables and WHOIS databases to find which Autonomous System announces the IP prefix containing that address. The result shows the ASN, the organization name, country, and all IP prefixes allocated to that network. This is useful for tracing who controls a suspicious IP, understanding which ISP or cloud provider hosts a service, or investigating network routing.
What is the difference between ASN and IP address?
An IP address identifies a specific endpoint (server, device, or network interface) on the internet. An ASN identifies the network organization that manages a group of IP addresses and controls how they are routed. Think of it like a postal system: an IP address is like a street address for a specific building, while an ASN is like the postal district that manages delivery for an entire area. One ASN can control anywhere from a small /24 block (256 IPs) to millions of IP addresses across many prefixes.
What is BGP and how does it relate to ASNs?
BGP (Border Gateway Protocol) is the routing protocol that determines how traffic flows between networks on the internet. Each Autonomous System uses BGP to announce which IP prefixes it controls and to learn routes to other networks. When you send data to an IP address, your ISP's BGP routing table determines the best path through multiple ASNs to reach the destination. BGP hijacking — where an attacker announces someone else's IP prefixes — is a serious security threat, which is why monitoring ASN routing data is important for network security.
How many ASNs exist on the internet?
As of 2025, there are over 80,000 active ASNs on the internet, with new ones being assigned regularly. The largest ASNs (by number of IP prefixes) belong to major ISPs and cloud providers. 16-bit ASNs range from 1 to 65535, while 32-bit ASNs (introduced to expand capacity) range up to over 4 billion. The ASN Lookup tool works with both formats.

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API Endpoint

POST /api/v1/network/asn
View Documentation