UUID Generator Online
Generate universally unique identifiers (UUIDs) online. Create random UUID v4 or time-based UUID v1 values, generate multiple UUIDs at once, and easily copy the results.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier used to uniquely identify information in computer systems. UUIDs are also known as GUIDs (Globally Unique Identifiers).
UUIDs can be generated independently without a central authority, making them useful for distributed systems, databases, APIs, and software applications.
A UUID is typically represented as 32 hexadecimal characters separated by four hyphens, following the format 8-4-4-4-12.
For example: 550e8400-e29b-41d4-a716-446655440000
Different UUID versions use different generation methods. This tool supports UUID v1 (time-based) and UUID v4 (random).
UUIDs are standardized in RFC 9562, which replaced the earlier RFC 4122 specification.
UUID Version 1 (Time-based)
UUID v1 generates identifiers using a timestamp, a clock sequence, and a 48-bit node identifier.
The timestamp represents the time of generation, while the clock sequence and node identifier help prevent duplicate UUIDs.
Traditionally, the node identifier was derived from the computer's MAC address. However, modern implementations can use a randomly generated node identifier to protect privacy.
Because UUID v1 may expose information about the generation time and the originating device, it is not recommended when this information must remain private.
For new applications requiring time-ordered identifiers, UUID v7 is generally a better alternative.
UUID Version 4 (Random)
UUID v4 generates identifiers using random or pseudorandom numbers. It is widely used in software applications because it does not require a timestamp or device-specific information.
A UUID v4 contains 122 random bits. The remaining 6 bits identify the UUID version and variant.
With 122 random bits, the probability of generating two identical UUIDs is extremely low when a reliable random number generator is used.
UUID v4 is suitable for database records, API identifiers, and other applications that require unique values without a central registration system.
UUID v1 vs UUID v4
UUID v1 and UUID v4 both generate 128-bit identifiers, but they use different methods.
| Feature | UUID v1 | UUID v4 |
|---|---|---|
| Generation method | Timestamp and node identifier | Random numbers |
| Contains timestamp | Yes | No |
| May expose device information | Yes | No embedded device identifier |
| Requires MAC address | No | No |
| Typical use | Legacy time-based identifiers | General-purpose unique identifiers |
Which UUID version should you use?
For most applications, UUID v4 is a good default because it is simple, widely supported, and does not embed timestamps or device identifiers.
UUID v1 may be useful for compatibility with existing systems that require time-based identifiers.
Frequently asked questions
What is the difference between UUID and GUID?
UUID stands for Universally Unique Identifier, while GUID stands for Globally Unique Identifier. The terms are often used interchangeably. GUID is particularly common in Microsoft technologies.
Can two UUIDs be identical?
Yes, UUID collisions are theoretically possible. However, correctly generated UUID v4 values have an extremely low probability of collision, making them suitable for most applications requiring unique identifiers.
How many characters are in a UUID?
A UUID contains 128 bits (16 bytes). In its standard hexadecimal representation, it has 32 hexadecimal characters and 4 hyphens, for a total of 36 characters.
Which UUID version should I use?
UUID v4 is a good choice for most applications requiring random unique identifiers. UUID v1 is mainly useful for compatibility with existing time-based systems. UUID v7 is worth considering for new applications that benefit from time-ordered identifiers.
Are UUIDs secure?
UUIDs are designed for identification, not authentication or access control. Even when generated using secure randomness, UUIDs should not be treated as passwords or authorization tokens.
Can a UUID be reversed?
UUIDs are identifiers, not encrypted data. Random UUID v4 values do not contain original data to recover. UUID v1 values contain information such as a timestamp and node identifier, which may be extracted.
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