Just Tool It
Just Tool It / CIDR Calculator
On-device — nothing uploaded

CIDR / IP Subnet Calculator

Subnet math for IPv4 and IPv6. Type a CIDR — get the network, broadcast, mask, host range and binary breakdown.

Subnet splitter

Split the current network into smaller equal-size subnets.

Why use CIDR Calculator in your browser?

Passwords, hashes, and secrets should never transit a backend. CIDR Calculator: Subnet math for IPv4 and IPv6. Type a CIDR — get the network, broadcast, mask, host range and binary breakdown. Server-side tools upload or log inputs. Just Tool It does not: it uses Web Crypto and local utilities so passwords and secrets never transit a backend. Close the tab and the working data is gone. That is zero-server processing and on-device security.

How to use CIDR Calculator

  1. Open the tool on this page — no account or email required.
  2. Add your input by dropping a file, pasting text, or filling the form fields.
  3. Adjust options if available (quality, format, ranges, etc.).
  4. Run the tool and download (or copy) the result. Nothing was uploaded to Just Tool It.

Frequently asked questions

Is my data uploaded when I use CIDR Calculator?
No. Just Tool It is a static web app. Your input is processed with Web Crypto and local utilities so passwords and secrets never transit a backend. You can verify in the browser Network panel: no file payloads are sent to our origin for processing.
Is this tool free? Do I need an account?
Yes, it is free. There is no sign-up, paywall, or trial. We do not create user accounts because we never receive your files.
Does it work offline?
After the page and any required libraries are cached (including via the service worker / PWA), many tools keep working without a network. Large optional engines such as FFmpeg.wasm or OCR models still need a one-time download.
How is this different from other free online tools?
Most free tools upload files to a cloud worker. Just Tool It emphasizes zero-server processing and on-device security: files stay in browser memory until you download the output and close the tab.