About Network Tools Online

Network Tools Online is a free collection of browser-based networking and IP utilities. Calculate IPv4 subnets, expand CIDR ranges, look up MAC vendors, parse user agents, query DNS records, and reference standard service ports — all in one place, all in your browser.

We built this for network engineers, SRE / DevOps, sysadmins, and anyone who occasionally needs to do quick subnet math without firing up a calculator app or trusting a random web service with the IP plan of their internal network.

What We Offer

Our current toolset:

  • IPv4 Subnet Calculator — Compute network, broadcast, mask, host count, and usable range from any CIDR.
  • CIDR to IP Range — Expand a CIDR block to its start and end IPs, with optional full enumeration for small ranges.
  • MAC Address Lookup — Identify the hardware vendor from any MAC's 24-bit OUI, using a curated subset of the IEEE registry.
  • User Agent Parser — Extract browser, engine, OS, and device info using ua-parser-js.
  • DNS Record Lookup — Query A, AAAA, CNAME, MX, TXT, NS, and SOA records via Cloudflare's DNS-over-HTTPS resolver.
  • Port Reference — Look up IANA service assignments for common TCP/UDP ports.

How It Works

Subnet math, MAC lookup, UA parsing, and port reference all run locally in your browser — the data sets are bundled into the page. The only exception is DNS Lookup, which sends the domain you enter to Cloudflare's public DoH resolver at cloudflare-dns.com.

Built on widely used open-source libraries: ip-num for accurate subnet arithmetic, ua-parser-js for UA detection, and a curated subset of the IEEE OUI registry for vendor identification.

Why Browser-Based?

Internal IP plans, MAC inventories, and DNS audits are often sensitive. Sending them to a third-party calculator service creates risk for no upside. Our tools do the math locally — your CIDRs and MACs stay on your machine.

Our Principles

  • Free, always — No premium tiers, no API keys, no rate limits.
  • No registration — Use any tool immediately, no account required.
  • Privacy-first — Subnets, MACs, and UAs stay local. DNS goes to Cloudflare only.
  • Built for operators — Copy buttons on every field, monospaced output, zero clutter.

If you have a network-related tool we are missing or found a bug, reach out via our Contact page.