IP & DNS
IP & DNS — 4 free browser-based developer tools including What Is My IP, IP Address Lookup and CIDR Calculator. Everything runs locally with no signup or uploads, so your data stays private and results are instant.
How to Use
- 1Start with the address you are on— What Is My IP shows the public IPv4 or IPv6 address the internet actually sees, which is the first thing to confirm when a firewall rule or an allowlist is not matching.
- 2Work the subnet out from the prefix— The CIDR calculator turns a prefix such as /26 into the network address, broadcast address, netmask and the exact usable host range and count, so you can split a block without arithmetic mistakes.
- 3Look an address up or convert it— IP lookup reports the network and region behind an address, and the IPv4 to IPv6 converter writes the mapped and 6to4 forms a dual-stack configuration needs.
Frequently Asked Questions
256 addresses, of which 254 are assignable: the first is the network address and the last is the broadcast address. The CIDR Calculator shows the range, the subnet mask and the usable host count for any prefix, so you can size a subnet before allocating it.
GeoIP is reliable at the country level and usually right at the city level, but it maps the ISP's registration rather than the device. A mobile or VPN connection can appear hundreds of kilometres away, which is exactly why What Is My IP is handy for confirming a VPN is actually active.
Yes. The IPv4-mapped form embeds it directly as ::ffff:192.0.2.1, and 6to4 notation wraps it inside 2002::/16. The converter shows both, in compressed and fully expanded form, and converts back when an IPv6 address really does carry an IPv4 one.