# is-local-address

> Check if an URL hostname is a local address, including support for [Bogon IP address](https://ipinfo.io/bogon) ranges.

## Why is-local-address?

Most solutions typically determine local IP addresses by checking DNS, which is slow and unreliable. This implementation uses the Bogon IP address specification for static validation, delivering:

- **5x faster** than alternative approaches (DNS-based)
- **100x smaller** bundle size compared to similar libraries
- **100% accuracy** on all RFC-defined private IP ranges
- **Zero dependencies** for core functionality
- **Supports IPv4 and IPv6** including edge cases and mapped addresses

Check the [benchmark](/benchmark) for detailed performance metrics comparison.

## How it works

Instead of performing DNS lookups or complex regex validations, `is-local-address` uses a static, efficient approach:

1. **No network calls** - Validates against RFC specifications offline
2. **Pure regex matching** - Optimized patterns for IPv4 and IPv6
3. **Minimal overhead** - Only ~100 bytes gzipped

This makes it ideal for:
- High-performance APIs and microservices
- Edge computing environments with limited resources
- Security checks that need to run frequently
- Any scenario where you need fast, reliable local IP detection

## Install

```bash
$ npm install is-local-address --save
```

## Usage

The method exported by default supports detection of both IPv4 and IPv6 addresses:

```js
const isLocalAddress = require('is-local-address')

isLocalAddress(new URL('https://127.0.0.1').hostname) // true
isLocalAddress(new URL('http://[::]:3000').hostname) // true
isLocalAddress(new URL('https://example.com').hostname) // false
```

You can also specify to just resolve IPv4:

```js
const isLocalAddress = require('is-local-address/ipv4')
isLocalAddress(new URL('https://127.0.0.1').hostname) // true
isLocalAddress(new URL('http://[::1]:3000').hostname) // false
```

or just IPv6:

```js
const isLocalAddress = require('is-local-address/ipv6')
isLocalAddress(new URL('http://[::]:3000').hostname) // true
isLocalAddress(new URL('https://127.0.0.1').hostname) // false
```

## License

**is-local-address** © [Kiko Beats](https://kikobeats.com), released under the [MIT](https://github.com/Kikobeats/is-local-address/blob/master/LICENSE.md) License.<br>
Authored and maintained by [Kiko Beats](https://kikobeats.com) with help from [contributors](https://github.com/Kikobeats/is-local-address/contributors).

> [kikobeats.com](https://kikobeats.com) · GitHub [Kiko Beats](https://github.com/Kikobeats) · X [@Kikobeats](https://x.com/Kikobeats)