UUID / GUID Generator

What is a UUID / GUID?

UUID stands for Universally Unique Identifier, and GUID stands for Globally Unique Identifier. These are 128-bit numbers used to identify computers, applications, services, and other objects. While sometimes used interchangeably, "GUID" is a term typically associated with Microsoft technologies, whereas "UUID" is the defined standard (RFC 4122) used across all platforms.

Why Version 4?

There are several versions of UUIDs, but Version 4 is the most common for modern applications. Here is how they differ:

• Version 1: Generated from the computer's MAC address and current time. This guarantees uniqueness but can leak privacy information (the time and location of creation).
• Version 4: Completely random or pseudo-random. This is the safest bet for most applications as it reveals no information about the creator and is virtually impossible to duplicate.
• Versions 3 & 5: Generated by hashing a namespace and name (using MD5 or SHA-1). These are deterministic; the same input always yields the same UUID.

The impossibility of Collisions

A UUID is 128 bits long, which means there are 2¹²⁸ possible values. That is approximately 3.4 × 10³⁸ combinations.

To put this in perspective: If you generated one billion UUIDs per second for the next 85 years, the probability of creating a single duplicate would be less than 50%. The number of possible UUIDs is vastly larger than the number of stars in the observable universe.

How to Use This Generator

1. Quantity: Enter how many UUIDs you want to generate (1 to 1000).
2. Formatting Options:
   • Hyphens: Include standard separators (e.g. c00813c8-599b...).
   • Braces: Wrap in curly braces (which is common in Microsoft/Windows environments).
   • Uppercase: Convert to uppercase standard.

UUID v4 Format Breakdown

A standard Version 4 UUID is represented as 32 hexadecimal digits, displayed in five groups separated by hyphens (8-4-4-4-12). It looks like this:

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

• x: Any hexadecimal digit (0-9, a-f).
• 4: The 13th digit is always '4', indicating the version number.
• y: The 17th digit is one of 8, 9, A, or B. This ensures the variant fits the standard.
• Total Length: 36 characters (32 alpha-numeric + 4 hyphens).

Common Use Cases

• Database Primary Keys: Unlike auto-incrementing integers, UUIDs allow you to generate IDs offline or in distributed systems without checking a central database, making database merges significantly easier.
• Session & Token IDs: Their randomness makes them unguessable, which is perfect for security tokens, cookie IDs, and API keys.
• Unique Filenames: When users upload files, renaming them to a UUID ensures no two files ever overwrite each other, even if they had the same original name.