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)
1 / 2 ^ 128 = 2.938735877055719e-39.
To name how small this number is, imagine that this number is 1 divided by the number,
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.