Why might my IP show as 100.64.x.x or report unexpectedly?

You're behind carrier-grade NAT. RFC 6598 (Weil, Kuarsingh, Donley, Liljenstolpe & Azinger, 2012) reserved 100.64.0.0/10 — known as the Shared Address Space — for ISPs to use on the customer side of CGNAT translation. Mobile networks and some fibre operators run customers behind CGNAT to conserve IPv4 addresses; multiple subscribers share a smaller pool of real public IPs. From the open internet's perspective you appear to share an IP with hundreds of others, which complicates IP-based blocking and authentication. Some VPN services also assign 100.64/10 internally. If you see this address as your 'public' IP, you can't typically port-forward or run public services on IPv4 from your home — but IPv6 is usually unaffected because IPv6 normally avoids CGNAT.

How accurate is the geolocation actually?

Accuracy depends on the IP type. Commercial GeoIP databases such as MaxMind GeoLite2 build their tables from regional registry filings (ARIN, RIPE, APNIC, LACNIC, AFRINIC) plus traceroute-derived geolocation and ISP-supplied data. ISP-fixed residential IPs are usually accurate to the city level because the registry filings include locale data per /24 block. Mobile IPs roam across regions — the same IP can appear in multiple cities within minutes — and CGNAT IPs may be reported at a regional aggregation point. Datacentre IPs (AWS, Hetzner, OVH) report the datacentre, not your physical location — which is why VPN exit nodes show the country/city of the VPN provider, not yours. Expect 50-200 km of slack for residential consumer IPs and significantly more for mobile/CGNAT/datacentre.

What Is My IP — IPv4, IPv6 & Location

Q: How does this tool detect my public IP?

The tool calls a public IP-info API (ipapi.co or ipify.org) which reads the source IP of the incoming TCP handshake on its server. That source IP is whatever endpoint terminates the connection on the public internet — for a residential customer it's typically your home router's WAN address, assigned by DHCP from the ISP. Behind that gateway your devices use RFC 1918 private addresses (10/8, 172.16/12, 192.168/16) translated by NAT. For mobile or CGNAT customers an extra translation tier (RFC 6598 100.64.0.0/10) sits between the LAN and the public IP. When traffic traverses a load balancer or reverse proxy that adds a Forwarded header (RFC 7239, Petersson & Nilsson, 2014), the original client IP is preserved through the chain so the API can see you, not the proxy — provided the proxy is configured to set the header correctly.

Q: Why are my IPv4 and IPv6 addresses different?

They're different addresses for different network protocols, allocated independently. IPv4 (RFC 791) uses 32-bit addresses; the global free pool effectively exhausted in 2011, leading to widespread NAT. IPv6 (RFC 4291) uses 128-bit addresses with vast address space and avoids most NAT — your device usually has a routable IPv6 address with a globally unique prefix from your ISP. A dual-stack network supplies both. Routing paths can differ: a query routed via IPv4 may transit different intermediate networks than the same query via IPv6, which is why latency and even GeoIP location may differ between the two stacks. Operationally, when you firewall or troubleshoot, treat them as two separate identities — a rule applied to your IPv4 doesn't apply to your IPv6 unless you configure both.

Q: What does the ASN tell me?

The Autonomous System Number (RFC 1930, Hawkinson & Bates, 1996) identifies the network operator that owns and announces the IP block. Each AS is a connected group of IP prefixes run by one or more network operators with a single, clearly defined routing policy — for example AS15169 belongs to Google, AS32934 to Meta, AS13335 to Cloudflare. ASNs are assigned by the regional registry that allocated the IP block and stay relatively stable; an ASN change usually means the operator transferred ownership or merged. From an ASN you can tell whether traffic comes from a residential ISP, a mobile carrier, a datacentre, a VPN provider, or a security scanner — this is more useful for fraud detection and traffic shaping than the IP itself, because IP-level geolocation is noisy but ASN identity is unambiguous.

Find My Public IP Address (IPv4 & IPv6)

This tool reports the public IP address that the internet sees when you make a connection — the value web servers, mail servers, and APIs log against your activity. Detection works by querying a public IP-info API (ipapi.co or ipify.org) which reads the source IP of the incoming TCP handshake; that is the address allocated to your router, or to your operator's CGNAT translator (RFC 6598 100.64.0.0/10). LANs internally use RFC 1918 private ranges (10/8, 172.16/12, 192.168/16) which never appear here — those addresses live behind NAT. The result includes IPv4 and IPv6 if your network supplies a dual-stack path (RFC 4291), the ISP organisational name and Autonomous System Number (RFC 1930 — assigned by the regional registry: ARIN, RIPE, APNIC, LACNIC or AFRINIC), an approximate geolocation derived from MaxMind's GeoLite2 GeoIP database, and a timezone hint. When traffic traverses a load balancer or reverse proxy that supports the Forwarded header (RFC 7239 Petersson & Nilsson, 2014), the original client IP is preserved through the chain so the API sees you, not the proxy. All output is rendered in your browser; the upstream API may log the request per its policy.

How to find your public IP

Open the page — your public IP is fetched automatically from a public IP-info API.
The tool displays IPv4 + IPv6 (if dual-stack), ISP organisational name, ASN, approximate geolocation, and timezone.
Copy the IP you need with the one-click copy button.
Use the result to debug network issues, configure a firewall allowlist, verify a VPN exit, or share with support.

Common use cases

Adding your current IP to a firewall allow-list for remote server access (SSH, RDP, jump host).
Verifying a VPN routes traffic through the expected exit country and ASN (provider's data centre).
Sharing your public IPv4 + IPv6 with support when troubleshooting a network issue.
Detecting whether your operator has placed you behind RFC 6598 CGNAT (100.64.x.x) which limits inbound services.

Frequently asked questions

How does this tool detect my public IP?

Calls a public IP-info API (ipapi.co or ipify.org) which reads the source IP of the incoming TCP handshake. That is your router's WAN address, or the CGNAT shared IP for mobile/CGNAT customers (RFC 6598 100.64.0.0/10).

Why are my IPv4 and IPv6 addresses different?

Different protocols, allocated independently — IPv4 (RFC 791) 32-bit addresses largely behind NAT, IPv6 (RFC 4291) 128-bit usually globally unique. Routing paths and even GeoIP location can differ between stacks.

Why does my IP show as 100.64.x.x?

You are behind carrier-grade NAT. RFC 6598 reserved 100.64.0.0/10 for ISP-side CGNAT — common on mobile and some fibre operators. Multiple subscribers share a smaller pool of real public IPs.

How accurate is the geolocation?

City-level for ISP-fixed residential blocks; 50–200 km off for mobile/CGNAT roaming; datacentre-only for cloud/VPN exits. ASN identification (RFC 1930) is more reliable than location.

What does the ASN tell me?

The Autonomous System Number identifies the network operator that owns the IP block (e.g. AS15169 = Google, AS13335 = Cloudflare). More useful than IP geolocation for fraud detection and traffic shaping.

Why your reported IP can differ from what you expect

The address an external server logs is whatever endpoint completes the TCP three-way handshake on the public internet. For a residential connection that is typically your home router's WAN address — assigned by DHCP from your ISP. Behind it lives an RFC 1918 private network (10/8, 172.16/12, 192.168/16) where each device has a separate local IP that NAT translates outward. For carrier-grade NAT customers (mobile, some fibre operators), there is an additional translation tier using RFC 6598 100.64.0.0/10 — the ISP-side CGNAT range — so multiple subscribers share a smaller pool of public IPs. Geolocation accuracy depends on IP type. ISP-fixed residential blocks usually map to city-level accuracy because regional registry filings include locale data; mobile and CGNAT IPs roam across regions and may report a city 50–200 km away. Datacentre IPs (AWS, Hetzner, OVH) report the datacentre, not your physical location. ASN identification (RFC 1930) is more reliable than location: a /24 block's ASN is unambiguous because BGP requires it. The Forwarded HTTP header (RFC 7239) standardises how proxies preserve the original client IP through a chain — `Forwarded: for=192.0.2.43;by=203.0.113.1` — replacing the older patchwork of vendor-specific headers like X-Forwarded-For. When this tool's API sees a Forwarded chain, it reports the original endpoint, not the proxy.

Public IPv4 + IPv6 dual-stack detection (RFC 4291)
Geolocation (city, region, country) from MaxMind GeoLite2
ISP organisational name + Autonomous System Number (RFC 1930)
Timezone + connection details (browser-side)
RFC 1918 private + RFC 6598 CGNAT range awareness
Forwarded HTTP header (RFC 7239) chain handling for proxied requests

Free. No signup. Browser tools (subnet, JWT, password strength) run locally; lookup tools query public APIs (Cloudflare DoH, RDAP, certificate logs). Full per-tool breakdown at /methodology/.

Sources (7)

Petersson, A., & Nilsson, M. (2014). Forwarded HTTP Extension. RFC 7239, IETF.
Postel, J. (1981). Internet Protocol. RFC 791, IETF (32-bit IPv4 addressing).
Hinden, R., & Deering, S. (2006). IP Version 6 Addressing Architecture. RFC 4291, IETF.
Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. J., & Lear, E. (1996). Address Allocation for Private Internets. RFC 1918, IETF (10/8, 172.16/12, 192.168/16).
Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., & Azinger, M. (2012). IANA-Reserved IPv4 Prefix for Shared Address Space. RFC 6598, IETF (100.64.0.0/10 CGNAT).
Hawkinson, J., & Bates, T. (1996). Guidelines for creation, selection, and registration of an Autonomous System (AS). RFC 1930, IETF.
MaxMind (live). GeoLite2 Free Geolocation Database. maxmind.com/en/geoip2-services-and-databases.

These are the IETF RFCs, NIST publications, and W3C standards the tool implements or queries. Locate them on the IETF Datatracker (datatracker.ietf.org) or the official standards body.