# Unique Local Addresses

**Unique local** IPv6 addresses are _private_ addresses that **cannot be used over the internet**.

You do not need to register to use them. They can be used freely within internal networks and don't need to be globally unique. Can't be routed over the internet.

{% hint style="info" %}
The global ID should be unique so that addresses don't overlap when companies merge.
{% endhint %}

Uses the address block FC00::/7 (FC00:: to FDFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF).

However, a later update requires the 8th bit to be set to 1, so the first two digits must be FD.

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