IPv4 Range Expander

The IPv4 Range Expander turns a compact IP range into the full, explicit list of every address it contains. Paste a CIDR block like 192.168.1.0/28 or a start-end range like 192.168.1.1-192.168.1.10, and the tool prints each address on its own line along with a total count you can copy or download.

How to use it

1. Enter a range in one of two forms:
   • CIDR notation — an address followed by a slash and a prefix length, e.g. 10.0.0.0/24. Any host bits in the address are masked down to the network, so 192.168.1.5/29 expands the whole 192.168.1.0/29 block.
   • Start-end range — two addresses joined by a hyphen, e.g. 172.16.0.1-172.16.0.50. The start must not be greater than the end.
   • A single address (192.168.1.5) simply expands to itself.
2. The expanded addresses appear immediately, one per line, with a running total.
3. Use the copy or download buttons to grab the list as a text file (ip-list.txt).

Why expand a range?

Firewall rules, allow-lists, monitoring targets, load-test host files, and DNS zone tooling often need every address spelled out rather than a subnet shorthand. Reading a /28 and writing out its 16 hosts by hand is slow and error-prone; expanding it programmatically guarantees the boundaries are right.

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) writes a network as an address plus a prefix length — the number of leading bits that identify the network. A /24 fixes the first 24 bits, leaving 8 host bits, so it holds 256 addresses (0–255 in the last octet). Each step down doubles the size: a /28 has 16 addresses, a /29 has 8, a /30 has 4. The address you supply is masked to the network boundary before expansion, so it does not matter which host inside the block you type.

Why is there a size limit?

A short prefix describes an enormous range: a /8 is over 16 million addresses and a /0 is the entire IPv4 space of roughly 4.3 billion. Generating those would freeze your browser or exhaust memory. To stay fast and safe, this tool caps expansion at 65,536 addresses — the size of a /16. Anything larger is rejected up front with a message telling you to narrow the range (use a /16 prefix or longer, or a smaller start-end span).

Does it validate my input?

Yes. Each octet must be 0–255 with no leading zeros, the CIDR prefix must be 0–32, and a start-end range must run in ascending order. Invalid input produces a clear inline error instead of a broken result.

Is my data private?

The expansion runs entirely in your browser. Your input never leaves your device, so it is safe to paste internal or sensitive network ranges.