# Is Base64 encoded UUID still unique?

The short answer is ** yes**.

## What is UUID or GUID?

UUID or GUID stands for universally unique identifier. It is a sequence of bytes that have a wonderful property: this sequence is unique. This sequence contains 128 bits of information, so the probability of finding a collision (of generating another UUID with the same value) is approximately `1 / 2 ^ 128 = 2.938735877055719e-39`

. To name how small this number is, imagine that this number is 1 divided by the number, that is `10 ^ 17`

(100 Quadrillions) times bigger than the number of stars in the Universe.

## How it relates to Base64 encoding

The Base64 encoding transforms every single input byte into associated output serie of bits. To be exact, every three 8-bit values translates into four 6-bit values (24-bit word). Literally, we can match exactly one 24-bit word of Base64 output to every 24-bit input.

This means, that we have a single representation for every single UUID/GUID. Thus, the Base64 encoded UUID is still unique.

Written by **Vladimir Ignatev**