Find the block. Check the list.
Verify an IPv4 subnet and compare candidate addresses by inclusive mathematical membership. All calculations stay in this tab; no device is contacted.
Address inputs
Ready for an address and prefix.
Edits clear results. Reset or reload discards all inputs and results.
Block analysis
A boundary, not a device check.
Enter an IPv4 address and prefix, then choose Analyze to reveal the complete inclusive block.
The example checks four addresses around a /26 block. Nothing is sent to those addresses.
Canonical network / prefix
Entered address · 32 bits
P = prefix bit · A = remaining address bit. The letters distinguish each bit as well as color.
Candidate decisions
| Line | Address | Decision | Boundary equality |
|---|
No candidates entered.
Complete selectable report
Select this text manually if saving is blocked. Downloads follow your browser settings.
Read the boundaries literally.
Both ends belong to the block. A /31 contains two addresses; a /32 contains one. No conventional network or broadcast reservations are inferred.
This is mathematical block membership only. It does not inspect devices, perform DNS or ping, allocate addresses, split subnets or recommend routes.
Inputs and results live only in volatile tab memory. No uploads, accounts, telemetry, storage APIs or permissions. Only clicking Download .txt requests a local UTF-8 file. Reset or reload discards everything.
Subnet questions
How do I check a subnet and an address list?
Enter one dotted-decimal IPv4 address and a separate prefix from 0 through 32, optionally paste up to 100 candidate addresses one per line, then choose Analyze. The results show the canonical block, masks, inclusive boundaries, address count and ordered Inside or Outside decisions. Blank lines are ignored and duplicates count separately.
What do /31 and /32 mean here?
Both boundaries are included. A /31 contains two addresses and a /32 contains one; its single address equals both boundaries. This is mathematical membership only. No network or broadcast reservations are inferred, and the app does not inspect devices or recommend routes.
Are my addresses uploaded or saved? Are permissions needed?
Inputs and results live only in volatile tab memory. No uploads, accounts, telemetry, storage APIs or permissions are used. No device is contacted. Only clicking Download .txt requests a local UTF-8 file. Reset or reload discards everything; downloaded files remain yours to manage.
How do I fix invalid input or recover a report?
Validation preserves all inputs. Use exactly four decimal octets from 0 to 255 without leading zeros; hostnames, IPv6, signs and shortened addresses are rejected. Candidate errors identify their source line. The entire candidate input is limited to 8192 UTF-8 bytes and 100 nonblank lines. Every edit clears results and disables export until successful analysis. Select the complete report if saving is blocked. Reset or reload cannot recover work.