Bulk UUID v4 Generator Tool
What is a UUID?
A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit number used to uniquely identify information in computer systems. The standard representation is a 32-character hexadecimal string, typically displayed in 5 groups separated by hyphens (8-4-4-4-12).
Understanding UUID Version 4
This calculator generates Version 4 UUIDs. Unlike Version 1 (which relies on the timestamp and MAC address), Version 4 is based primarily on random numbers. This makes it ideal for generating IDs where privacy is a concern or where sequential generation is not required.
The structure of a standard v4 UUID is defined as follows:
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
Where:
- x is any hexadecimal digit (0-9, a-f).
- 4 indicates the version number (Version 4).
- y is one of 8, 9, A, or B (variant bits).
Probability of Collision
The primary concern with random identifiers is the risk of "collision" — generating the same UUID twice. However, with 128 bits, the total number of unique keys is $$ 2^{128} \approx 3.4 \times 10^{38} $$.
For Version 4 UUIDs, 6 bits are fixed (for version and variant), leaving 122 random bits. The number of possible v4 UUIDs is:
$$ 2^{122} \approx 5.3 \times 10^{36} $$
To put this in perspective, you would need to generate 1 billion UUIDs per second for about 85 years to have a 50% probability of a single collision. For all practical purposes in database keys, session tokens, and transaction IDs, UUID v4 is considered unique.
Best Practices
- Database Keys: UUIDs are excellent for distributed databases where auto-incrementing integers are difficult to synchronize.
- Performance: While safe from collisions, storing UUIDs as strings (CHAR 36) can be less efficient than binary formats (BINARY 16).
- Security: Since v4 UUIDs are random, they cannot be predicted, making them suitable for non-critical security tokens (though cryptographically secure random number generators should always be used).