# IPv6 ULA Generator

URL: https://phishdestroy.io/developer-tools/ipv6-ula-generator
Category: General dev
Where it runs: Runs locally (nothing you enter is uploaded)

Get a private IPv6 prefix for a home lab, VPN or internal network that is very unlikely to clash with anyone else's, as RFC 4193 intends.

## Example input

Subnet 0010

```
0010
```

A random fdXX:XXXX:XXXX::/48, its subnet fdXX:XXXX:XXXX:0010::/64 and a random host address inside it; the Global ID changes on every run.

## FAQ

### How is the prefix built?

fd (the locally assigned half of fc00::/7) plus a 40-bit Global ID from crypto.getRandomValues forms the /48, your 16-bit subnet ID forms the /64, and the example host part is 64 random bits. RFC 4193 suggests deriving the Global ID from a SHA-1 hash of the time and a machine identifier, but its requirement is a pseudo-random value, which this is.

### What should I enter as the subnet ID?

Up to four hex digits, 0000 to ffff, which gives 65,536 possible /64 networks inside the /48; shorter values are padded with leading zeros. The field is not checked, so a non-hex value such as zz produces an invalid address.

### Is anything sent or registered?

No. The prefix is generated in your browser and nothing is uploaded; unique local addresses need no registration.

## Related tools

- [IPv6 Expander & Compressor](https://phishdestroy.io/developer-tools/ipv6-compressor)
- [CIDR / Subnet Calculator](https://phishdestroy.io/developer-tools/cidr-subnet-calculator)
- [MAC Address Generator](https://phishdestroy.io/developer-tools/mac-address-generator)
- [IPv4 Range Expander](https://phishdestroy.io/developer-tools/ipv4-range-expander)

All tools: https://phishdestroy.io/developer-tools