CIDR / Subnet Calculator
Full subnet breakdown from any CIDR notation.
Runs 100% in your browser — nothing is ever uploaded.
What is CIDR?
Calculate network address, broadcast, host range and usable IPs from any CIDR block. Free subnet calculator, client-side. Enter a value and watch the result update instantly — no waiting and no page reloads. Free and unlimited, with no watermarks and no registration — all processing happens right in your browser, so nothing is ever sent to a server.
How to use CIDR
- Open CIDR — it runs instantly in your browser.
- Enter your value or adjust the interactive controls.
- The result updates in real time as you type.
- Copy the result with one click and use it anywhere.
NetScope FAQ
Is CIDR really free?
Yes — CIDR is 100% free with no limits, no watermarks and no registration. You can use it as often as you like, on as many files or inputs as you need.
Is my data safe when I use CIDR?
Absolutely. CIDR runs entirely in your browser using JavaScript — your input is processed on your own device and is never uploaded to any server.
Does CIDR work on mobile devices?
Yes. CIDR works in any modern browser on desktop, tablet and mobile (Chrome, Firefox, Safari, Edge) — there is no app to install.
Are these network tools free?
Yes — every NetScope tool is 100% free with no signup, no limits and no ads walls.
Is my data uploaded anywhere?
No. All calculations (CIDR math, URL parsing, UTM building) run entirely in your browser. Nothing ever leaves your device.
Do these tools work offline?
Yes — once the page is loaded, the calculators work without an internet connection.
Can I use NetScope on private or internal addresses?
Yes, and that is the main reason it exists. Subnet, binary and URL tools are pure calculation, so RFC 1918 ranges like 10.0.0.0/8 or 192.168.1.0/24, internal hostnames and staging URLs are handled exactly like public ones — and never leave your browser. The ping and WebSocket testers are the one exception: they open a real connection, so they only reach hosts your own machine can already reach.
How accurate is the ping test compared with the ping command?
It measures something slightly different. A terminal ping sends ICMP packets, which browsers cannot emit, so NetScope times an HTTP request instead. The result therefore includes DNS resolution, the TLS handshake and the server’s own response time, and reads higher than ICMP. That makes it a good proxy for what a visitor experiences, but not a substitute for ICMP when you are diagnosing packet loss.
Do I need to install anything or sign in?
No. Every NetScope tool is plain JavaScript served with the page — no account, no extension, no CLI. Bookmark the tool you use most and it opens ready to work, on a phone, a locked-down work laptop or a machine where you cannot install software.