IP in Subnet Checker

Check if a given IP address belongs to a specific subnet/CIDR range with batch checking support.

Tested tool guide Tested browser tools Checked August 16, 2026

What IP in Subnet Checker does and how it behaves

Enter a subnet in CIDR notation and one IP address or a batch of addresses. The checker compares every candidate with the numeric address range selected by the CIDR prefix and identifies which candidates belong to that subnet. It answers a containment question, not whether an address is assigned, reachable, private, trusted, or allowed through a firewall. A frequent surprise is that IPv4 network and broadcast addresses are numerically inside their CIDR block, even when they are not available as ordinary host addresses.

How the result is produced

CIDR comparison

A CIDR such as 192.0.2.0/24 combines an address with a prefix length. The checker uses that length to determine which leading address bits identify the subnet, then compares them with the corresponding bits of each candidate. A match means the candidate falls between the CIDR block's first and last numeric addresses, inclusive.

Independent batch checks

Batch checking applies the same subnet test independently to every candidate; it does not merge candidates or compare them with one another. A pasted list can therefore produce a mixture of inside and outside results. An invalid IP literal, a missing CIDR prefix, or incompatible address families cannot provide a meaningful membership decision and should be corrected before interpreting the results.

Good uses

Check a list of client addresses against the CIDR supplied for a reverse proxy, VPN, or firewall allowlist before changing its configuration.
Verify that proposed static addresses or recorded device addresses fall within the subnet assigned to a particular network segment.
Filter incident-response addresses conceptually by testing whether log entries belong to a provider, office, service, or infrastructure CIDR under investigation.

Limits and checks

Inside the subnet does not mean usable by a host. The result includes every numeric address in the block, including boundary addresses that may have special roles.
The slash number counts fixed leading bits, not addresses. In IPv4, /24 leaves 8 varying bits and therefore covers 256 numeric addresses, not 24.
Membership is relative only to the CIDR entered. An adjacent subnet, a broader parent block, a hostname, and an organization's claimed ownership are not implied by a positive or negative result.

Common questions

Does a match mean the address is reachable?

No. The check establishes only that the IP address belongs to the numeric interval represented by the CIDR. It does not contact the address or inspect routes, firewall policy, service state, DNS, or address assignment. A matching address can still be unused, unreachable, disconnected, or blocked.

Are IPv4 network and broadcast addresses considered inside the subnet?

Yes, when those addresses are part of the selected IPv4 CIDR block, numeric containment includes them. That does not mean they are available for assignment to an ordinary host. Host usability depends on the subnet and operating context, while this checker answers the narrower question of whether the address lies within the block.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.