GUID stands for globally unique identifier.

GUIDs are usually stored as 128-bit values, and are commonly displayed as 32 hexadecimal digits with groups separated by hyphens.

Here is an example {21EC2020-3AEA-4069-A2DD-08002B30309D}.

They may or may not be generated from random (or pseudo-random) numbers.

GUIDs generated from random numbers normally contain 6 fixed bits (these indicate that the GUID is random) and 122 random bits; the total number of unique such GUIDs is 2^{22} (approximately 5.3×10^{36}).

The probability of the same number being generated randomly twice is negligible;

Assuming uniform probability for simplicity, the probability of one duplicate would be about 50% if every person on earth as of 2014 owned 600 million GUIDs.

WARNING

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Do not use this way as it will only return with all zeros as shown below.

`Guid g1 = new Guid(); // g1 will return 00000000-0000-0000-0000-000000000000`

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Here is the correct wayGuid g1 = Guid.NewGuid(); //`g1 will return a proper GUID like {21EC2020-3AEA-4069-A2DD-08002B30309D}`