What is the IPv6 private address range?

What is the IPv6 private address range?

• fe80:0000:0000:0000 - feff:ffff:ffff:ffff
• ffc0:0000:0000:0000 - ffef:ffff:ffff:ffff
• fd00:0000:0000:0000 - fdff:ffff:ffff:ffff
• fec0:0000:0000:0000 - feff:ffff:ffff:ffff 

EXPLANATION

Here is a unique private IPv6 address range generated just for you (refresh page to get another one):

Prefix/L:	fd
Global ID:	2aec802d69
Subnet ID:	d701
Combined/CID:	fd2a:ec80:2d69:d701::/64
IPv6 addresses:	fd2a:ec80:2d69:d701:xxxx:xxxx:xxxx:xxxx

If you have multiple locations/sites/networks, you should assign each one a different "Subnet ID", but use the same "Global" ID for all of them.
The IPv6 address space is so huge (2¹²⁸) that everyone should be able to get a public IP address for every device they will ever own. So theoretically it shouldn't be necessary to have private IPv6 addresses like the 192.168.x.x and 10.x.x.x addresses in IPv4.

However until you can actually get an IPv6 address range from your ISP, you may want to use "private" addresses for internal networks and testing etc.
In IPv6 there is a special "Unique Unicast" IP range of fc00::/7 which should be used for this as per RFC4193.
The official definition looks like this:

| 7 bits |1| 40 bits | 16 bits | 64 bits | +--------+-+------------+-----------+----------------------------+ | Prefix |L| Global ID | Subnet ID | Interface ID | +--------+-+------------+-----------+----------------------------+

In practice such address will always start with "fd" because the 8th (L) bit must be one.
The "Global ID" and "Subnet ID" must be random to ensure uniqueness (which is what this page does).
You are free to assign addresses from the rest (Interface ID).

Please note:
A former standard proposed the use of so-called "site-local" addresses in the fec0::/10 range.
This has been deprecated (see RFC3879) and should no longer be used.