cidr-to-regex

Convert IPv4 and IPv6 CIDR blocks into regular expressions.

Install

pnpm add cidr-to-regex

Usage

import { cidrToRegex } from "cidr-to-regex";

const regex = cidrToRegex("2001:db8::/48");
const ok = regex.test("2001:0db8:0000:0000:0000:0000:0000:0001");

API

cidrToRegex(cidr: string, options?: CidrToRegexOptions): RegExp

type CidrToRegexOptions = {
  anchored?: boolean; // default false
  ignoreCase?: boolean; // default false
  global?: boolean; // default false
};

• Accepts IPv4 and IPv6 CIDR input.
• CIDR parsing is liberal (for example compressed IPv6 like ::ff/16 and IPv4 inet_aton shorthands like 10.1/32 are accepted).
• CIDR network bits are normalized (host bits in the input address are ignored).
• By default, returned regex is not full-string anchored.
• options.anchored controls whether ^...$ anchors are included.
• options.ignoreCase enables case-insensitive IPv6 matching (adds i flag).
• options.global adds the g flag to the returned regex.
• Output matching targets:
  • IPv4: canonical dotted-decimal (a.b.c.d, no leading zeros).
  • IPv6: canonical RFC 5952 text representation, including IPv4-mapped IPv6 addresses

Compatibility

• Node.js: >=14
• Browser compatibility with default options (anchored: false):
  • Chrome 67+
  • Firefox 78+
  • Safari 16.4+
• Browser compatibility with anchored: true (no regex lookbehind requirement):
  • Chrome 67+
  • Firefox 68+
  • Safari 14+

Development

pnpm install
pnpm run check

Linting and formatting:

pnpm run lint
pnpm run lint:fix
pnpm run format
pnpm run format:check

Fixture generation

pnpm run generate:fixtures
pnpm run generate:differential-fixtures

These scripts use Python's ipaddress module to generate deterministic test fixtures. The generated fixtures are committed; test execution itself is pure TypeScript.

Benchmark

pnpm run bench

Optional environment variables:

• BENCH_ITERS (default 5000)
• BENCH_WARMUP (default 300)