IP to ASN

Look up the ASN of many IPs

Paste a list of IPv4 or IPv6 addresses to see which network prefix each one sits in and which ASN (autonomous system) announces it. Based on public BGP routing data.

What an IP to ASN lookup shows

An ASN answers "which network announces this IP?", which helps when you analyze traffic or build lists of ranges to allow or block.

What an ASN is
An ASN (autonomous system number) identifies a network that is run as one unit on the internet, such as an ISP, a cloud provider or a large organization. One ASN usually announces many IP prefixes (like 8.8.8.0/24).
What you get for each IP
The network (the matching routed prefix), the ASN, the AS name and holder, and the country where the AS is registered. IPv4 and IPv6 both work, up to 100 per lookup. Copy the table into a spreadsheet or export a CSV with a header row.
Where the data comes from
We ask RIPEstat how each IP appears in the global BGP routing table. The registration country comes from the allocation records published by the regional internet registries (RIRs) and is cached for 24 hours per AS. It's based on public information and tells you who announces the address and where they registered, not where the IP is.
What it can and can't tell you
It shows which network an IP belongs to, which suits log analysis, allowlists and tracing attacks. It can't show the exact location or what the address is used for. Addresses that are not announced, and private addresses, have no result. Routes change over time, and a prefix can be announced by more than one ASN. There is no domain column because public routing data doesn't contain that.

How to look up ASNs for a list of IPs

Paste the IPs straight from your logs, spreadsheet or chat into the text box. Commas, spaces, tabs and line breaks can be mixed. To try it first, click "Fill in an example".
Under the box you'll see "IPs recognized: N". IPv4 and IPv6 are both detected and duplicates count once. Over 100, click "Keep the first 100" and submit the rest in batches.
Click "Look up all". Each IP is checked once against public routing data; IPs checked within the last hour come from cache. Private and reserved addresses are not looked up, and their rows say why.
Read each IP's network, ASN, AS name and registration country in the table. When a prefix is announced by several ASNs they are joined with a slash, up to 3.
Click "Copy table" to paste into a spreadsheet, or "Export CSV". The CSV has a header row and a fixed column order: ip, network, asn, country_code, name, org, error.

Result columns explained

The CSV splits out one more column, org, than the screen and adds an error column at the end. For rows that couldn't be found, the other columns are empty.

IP: The recognized, de-duplicated address, in the order it first appeared in your text.
Network (network): The matching routed prefix, such as 8.8.8.0/24. It can be a wider parent prefix than you expect, because it is the block actually announced in the routing table.
ASN (asn): The autonomous system number that announces the prefix, written like AS15169. When several origin ASes announce the same prefix they are joined with a slash, up to 3.
AS name (name): The first part of the holder text, usually the network's short name such as GOOGLE or CLOUDFLARENET. The screen shows the holder text in full.
Organization (org, CSV only): The organization part of the holder text "short name - organization", such as Google LLC. Empty when the holder text has no " - " separator.
AS registration country (country_code): The country where this AS is registered with its regional internet registry (two-letter code such as US); with several origin ASes, the first one is used. It is not where the IP is: a global network's IPs can be spread over many countries. Left out when it can't be fetched.
Domain: There is no such column. Public routing data has no main domain for an AS, and we don't guess or make one up.
error (CSV only): The reason category for a failed row: invalid_ip, private_ip, not_announced (public address that isn't announced in routing), daily_limit, busy (data source busy), unavailable. Empty for successful rows.

IP to ASN FAQ

How do I find which ASN an IP belongs to?

Paste the IPs (one or many) into the box and click "Look up all". The ASN column is the autonomous system that announces the block the IP sits in, next to the AS name and holder. It works the same for a single IP.

Are there limits, and why?

Up to 100 IPs per lookup, 3 submissions a minute, and 500 uncached IPs a day per visitor; IPs looked up within the last hour come from cache and don't count towards the 500. The data comes from RIPEstat's free public API and we don't want to overload it, so we cap the volume.

Why does a row have no result?

Common reasons: the text isn't a valid IP; it is a private or reserved address that isn't in public routing; it is a public address that is currently not announced, so public routing data has nothing for it; today's uncached lookups ran out; or the data source was busy or didn't respond. Rows that were found are not affected, and you can resubmit the failed ones later.

Is the "AS registration country" the country the IP is in?

No. It's the country where the AS is registered with its regional internet registry, which says where the network holder is registered, while the IP can be used anywhere in the world. For an estimated location of the IP, use the bulk IP location tool.

How is this different from bulk IP location, and why no domain column?

This tool answers who announces an address: the routed prefix, ASN and holder, from public BGP data. The location tool gives estimated country, city and time zone from a different data provider, and the two have separate allowances. A domain would need another data source that public routing data doesn't offer, so we don't provide one.

Are the IPs I submit stored?

We don't keep a lookup history or link lookups to your account. The IPs are sent to RIPEstat to get the result, and results stay in server memory for up to an hour (24 hours for an AS's country). The text you paste is only parsed in your browser to find IPs; the rest isn't uploaded.