ASN Lookup
Identify and retrieve detailed information about Autonomous System Numbers (ASN), including organization names, countries, and assigned IP ranges.
Looks up live data What you enter is sent to our server to fetch live results from public sources. Results are cached briefly.
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About this tool
An Autonomous System Number (ASN) identifies the network that announces an IP address on the internet. Enter an IPv4 address and the tool queries Team Cymru's public IP-to-ASN service through DNS-over-HTTPS, then shows the AS number and name, the announced prefix, the country code, the regional registry and the allocation date. The lookup is made by our server and results are cached for an hour. Only IPv4 addresses are accepted; IPv6 and hostnames are not supported here, so resolve a hostname to an IP first.
How to use it
- Enter an IPv4 address such as 8.8.8.8.
- Press Look up ASN.
- Read the AS number, name, prefix and country.
- Use the prefix to see the full range that network announces.
Example
Google Public DNS belongs to Google's network, AS15169, which announces the range 8.8.8.0/24.
8.8.8.8
ASN: AS15169 Name: GOOGLE - Google LLC, US Prefix: 8.8.8.0/24 Country: US Registry: arin
What is an ASN?
The internet is made of tens of thousands of separately run networks: internet providers, hosting companies, clouds, universities and large companies. Each one is an autonomous system with its own number, such as AS15169 (Google) or AS13335 (Cloudflare). Networks use BGP to announce the IP ranges (prefixes) they serve, and the ASN tells you which network announces the range an address belongs to.
ASNs are handed out by the five regional internet registries: ARIN (North America), RIPE NCC (Europe, the Middle East and Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America and the Caribbean) and AFRINIC (Africa).
What an ASN lookup is used for
- Abuse reports
- Find the network a spamming or attacking IP belongs to, then contact that provider. The abuse address is in the registry's record for the IP.
- Firewall and allowlist rules
- The prefix shows the whole range a network announces, which helps when a service's addresses move around inside it.
- Server or person?
- An IP in a cloud or hosting network (for example Amazon AS16509, Microsoft AS8075 or DigitalOcean AS14061) usually means a server, VPN or bot rather than someone at home.
- Who really serves a site
- Look up a website's IP to see whether it is hosted directly or sits behind a CDN such as Cloudflare.
Common problems
- It asks for a valid IPv4 address
- Enter four numbers from 0 to 255 separated by dots. Hostnames and IPv6 addresses are rejected.
- The AS name is empty
- The name comes from a second lookup that can fail. The AS number and prefix from the first lookup are still valid.
- The country is not where the server physically is
- The country is the registry's record for the prefix, not a physical location.
Frequently asked questions
Can I look up an AS number instead of an IP?
Not here: the tool takes an IPv4 address. For details of an AS number itself, such as all its prefixes, use the registry's records or a BGP looking glass.
Does an ASN identify a person?
No. It identifies the network operator, such as an internet provider or hosting company, not the person using the address.