CIDR calculator

Everything is computed in your browser, by the scripts listed below. What you type never leaves this page.

Enforced by your browser

This page's Content Security Policy allows a single destination, the site's audience measurement (connect-src https://stats.r-no.fr, see below), and forbids any form submission (form-action 'none'). You can read the policy at the top of the page source.

Audience measurement

Like every page of the site, this one counts its visit with Umami, installed on R-no’s own server (stats.r-no.fr). It receives the address of the page, without parameters or anchor, the site you came from (its domain only), your browser, system, language and screen size, and the country, region and city deduced from your IP address, which is not kept. It never receives what you type, nor the result of the tool. No cookie, nothing stored in your browser; if your browser asks not to be tracked (Do Not Track), nothing is measured. The data is erased after 25 months.

• /commun/mesure.js: the filter applied before each sending, written for R-no Toolbox. 1.4 kB
  SHA-256 225eec74fd12623d82fc05ee7d222be629ce454d081c129e8d1e249ed37ee716
• https://stats.r-no.fr/m.js: Umami’s tracker, open source (MIT), served by the measurement server. Its fingerprint is not shown here: it changes with each version of Umami, and you cannot check from your browser that it is the published code. For that part, you have to trust R-no.

What is stored

No cookie, and nothing in the address. What you type is not kept. Your language is given by the address itself (/en/ or /fr/): nothing is stored to remember it. Like any website, the server records the download of the page and its files in its access logs (IP address, date and time, address requested, browser name). It never receives what you type.

Code that runs here

• app.js: the calculator, written for R-no Toolbox. Not minified, no third-party library. IPv4 and IPv6 use the same arithmetic on 32- and 128-bit integers (BigInt). 12.9 kB
  SHA-256 2f26e62b357a9494cb132fde18c7b860d5e705902d0c532364c8068dabf5834b
• textes.js: the French messages of the tool, shown by its script (the rest of the French page is written into its HTML when the site is built). It only defines texts, with no logic. 5.1 kB
  SHA-256 d6fc6621c65d6b71645447778121f431d1b4e974c366d89c0822f464ee2a0c98
• /commun/langue.js: the language helper, the same on every page of the site. It reads the language of the page and gives the tool its messages in that language. It stores nothing. 1.6 kB
  SHA-256 80f76f69773ef628d36d09bf8387cfedebda4529210d7120649b6f5603310631

Tested

The arithmetic is covered by automated tests, run on every deployment: /31 and /32 ranges, /0, IPv6 compression (RFC 5952), IPv4 inside IPv6, and the rejection of malformed input.

Check it yourself

Download a script and compare its fingerprint with the one above:
curl -s https://r-no.fr/ip/cidr/app.js | shasum -a 256

Limits

The full list is shown up to 65,536 addresses (an IPv4 /16, an IPv6 /112). In IPv4, the first and last addresses of a range up to /30 are counted as network and broadcast, and are not usable by hosts; /31 and /32 follow RFC 3021. IPv6 has no broadcast. The range type comes from the usual IANA special-purpose registries, not from a live lookup.