IP in Subnet Checker
Check whether an IPv4 address falls inside a given CIDR subnet or range. Test one address or a whole list — instantly, and entirely in your browser.
192.168.1.0/24.
What this tool does
An IP-in-subnet check answers one simple but constant networking question: does this address belong to that block? Firewalls, access-control lists, routing tables, and cloud security groups all make decisions by testing whether a source or destination IP falls inside a CIDR range. This checker performs the same test — a range comparison of 32-bit integers — and shows the supporting math so you can trust the result.
Give it a subnet in CIDR notation such as 10.0.0.0/16. The tool derives the network address (the lowest address in the block), the broadcast address (the highest), and then reports whether each IP you supply sits within that inclusive range. For example, 10.0.5.7 is inside 10.0.0.0/16 because it lies between 10.0.0.0 and 10.0.255.255, whereas 10.1.0.1 is outside it.
Apply the subnet mask to the IP with a bitwise AND. If the result equals the subnet's network address, the IP is in the block. Equivalently, the IP's integer value must be greater than or equal to the network address and less than or equal to the broadcast address. Both approaches always agree.
Understanding the mask is the key to reading any result. If you are new to prefixes and masks, our guide to what a subnet mask is explains how a /16 or /24 maps to 255.255.0.0 or 255.255.255.0. And if you are wondering why some blocks such as 10.0.0.0/8 never appear on the public internet, our reference on reserved IP addresses covers the private and special-use ranges.
Because the whole computation runs client-side, you can safely paste internal addressing plans without anything leaving your machine. Need to work the other way — turning a start and end address into blocks, or squashing many blocks into few? Try the CIDR Aggregator or convert a prefix to its inverse with the Wildcard Mask Calculator.
Frequently asked questions
How do I know if an IP is in a subnet?
Convert the IP and the subnet's network address to 32-bit integers, apply the subnet mask, and check whether the IP falls between the network address and the broadcast address. This tool does exactly that: 10.0.5.7 is inside 10.0.0.0/16 because it sits between 10.0.0.0 and 10.0.255.255, while 10.1.0.1 is not.
Can I check multiple IP addresses at once?
Yes. Paste one IP address per line in the addresses box and the checker will list each one as IN or OUT of the subnet you entered, so you can audit an allow-list or firewall rule in a single pass.
Does the network or broadcast address count as being in the subnet?
This tool treats the whole block as in the subnet, including the network and broadcast addresses. Containment is a mathematical range test, so every address from the network address through the broadcast address returns IN, even though the first and last are not usable host addresses.
Is my IP data sent to a server?
No. The check runs entirely in your browser with JavaScript. Nothing you type is uploaded, logged, or shared, so it is safe to test internal or sensitive addresses offline.
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