BYTETOOLS

IP in Subnet Checker

Check whether IP addresses fall inside one or more CIDR subnets. Batch-check whole lists with a per-IP match table — free, private and in-browser.

2
Inside a subnet
1
Outside all subnets
0
Invalid lines

Per-IP results

IP addressResultMatching subnet(s)
192.168.1.20 inside192.168.1.0/26
192.168.1.100 outside—
10.1.2.3 inside10.0.0.0/8

What is the IP in Subnet Checker?

The IP in Subnet Checker answers the everyday question "is this IP address inside this subnet? " — for one address or a whole list at once.

  • Batch mode: many IPs against many subnets in one pass
  • Shows every matching CIDR block per address, not just the first
  • Inside / outside / invalid summary counts at a glance
  • Invalid subnet lines reported without stopping the check
  • Copyable tab-separated results for spreadsheets
  • 100% client-side masking math — nothing is uploaded

How to use the IP in Subnet Checker

  1. 1

    Paste the IP addresses you want to check, one per line.

  2. 2

    Paste one or more subnets in CIDR notation, one per line.

  3. 3

    Read the per-IP table: inside or outside, with every matching subnet listed.

  4. 4

    Use the summary stats and Copy results for reporting.

About the IP in Subnet Checker

The IP in Subnet Checker answers the everyday question "is this IP address inside this subnet?" — for one address or a whole list at once. Paste your IPs on the left, your CIDR blocks on the right, and get a per-IP table showing inside or outside plus exactly which block matched.

The check is the same one routers perform: both the address and the subnet are masked to the prefix length and compared. That makes it dependable for verifying firewall rules, debugging "why is this client not matching my allowlist" mysteries, and auditing exported IP lists against expected ranges.

Both lists are processed entirely in your browser using 32-bit integer math. No address you paste is ever transmitted, so it is safe to check real client IPs and internal ranges.

Frequently asked questions

How do I check if an IP address is in a subnet?

AND both the IP and the subnet's network address with the subnet mask; if the results are equal, the IP is inside. For example 192.168.1.20 masked to /26 gives 192.168.1.0, matching the 192.168.1.0/26 network — so it is inside.

Can I check a list of IPs against several subnets at once?

Yes. Every pasted IP is tested against every pasted CIDR block, and the table lists all blocks each address falls into. Overlapping subnets are handled naturally — you simply see multiple matches for that IP.

Is 192.168.1.100 inside 192.168.1.0/26?

No. A /26 spans 64 addresses, so 192.168.1.0/26 covers .0 through .63. Address .100 falls in the next-but-one block, 192.168.1.64/26 covers .64–.127 — which is where .100 actually lives.

Does the checker count the network and broadcast addresses as inside?

Yes — membership is a pure prefix match, and the network and broadcast addresses are part of the block. Whether a device may be assigned those addresses is a separate question from whether they belong to the subnet.

Is it safe to paste production IP addresses here?

Yes. The comparison is done with local integer arithmetic in your browser tab; no server receives your lists, and the tool works even when you are offline.

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