Free calculators and utilities for network engineers — no signup, no gate. If you need more than a quick check, that’s what the paid engagements below each tool are for.
Subnet & CIDR Calculator
Instant network address, broadcast, usable range, and host count — plus a VLSM splitter for breaking a block into right-sized subnets.
Open tool →PAC File Parser & Tester
Paste or upload a .pac file and test a real URL against its actual FindProxyForURL() logic — see the resolved PROXY or DIRECT result.
Open tool →Network Mapper & Planner
Sketch a VLSM-based network layout from named segments, or check what your own browser can see about its current connection.
Open tool →