A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal digits in five groups separated by hyphens: 8-4-4-4-12. UUIDs are designed to be globally unique without requiring a central authority — the probability of generating two identical UUIDs is astronomically small.

UUID v4 generates identifiers using random or pseudo-random numbers. 122 of the 128 bits are random, with 6 bits reserved for version and variant indicators. V4 is the most commonly used version because it requires no external state or coordination.

When should I use UUIDs vs auto-increment IDs?

Use UUIDs when you need globally unique IDs across distributed systems, when IDs must be generated client-side, or when sequential IDs would expose information about your system. Use auto-increment IDs for simple single-database applications where sequential ordering is useful.

UUID Generator - Free Online Tool | Ultimate Design Tools

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier designed to be globally unique without a central authority. Formatted as 32 hex digits in a 8-4-4-4-12 pattern (like 550e8400-e29b-41d4-a716-446655440000), UUIDs are used as database primary keys, session tokens, file names, API identifiers, and distributed system IDs.

UUID Versions

v1 — based on timestamp + MAC address. Sortable by time but reveals device identity. v4 — fully random. Most commonly used. No external state needed. v5 — deterministic hash from a namespace + name. Same inputs always produce the same UUID. v7 (newest) — timestamp-ordered random UUID. Sortable like v1 but without revealing device info.

How to Use This UUID Generator

Click Generate — Click the generate button to create a new UUID instantly. Each one is cryptographically random and globally unique.
Choose the version — Select UUID v4 (random, most common), v1 (timestamp-based), or other versions depending on your requirements.
Copy the UUID — Click Copy to grab the UUID in standard format (8-4-4-4-12 hex digits separated by hyphens).
Generate in bulk — Need multiple UUIDs? Set the quantity and generate a batch of unique identifiers at once.

Tips and Best Practices

→ UUID v4 is the safe default. Version 4 UUIDs are generated from random data, making them suitable for most use cases — database primary keys, session IDs, file names, and API identifiers.
→ UUIDs are practically unique. With 122 random bits, UUID v4 has a collision probability so low that you'd need to generate 2.71 × 10^18 UUIDs to have a 50% chance of a single duplicate. For all practical purposes, they're unique.
→ Consider ULIDs for sortable IDs. If you need IDs that sort chronologically (useful for database performance), consider ULIDs — they're timestamp-prefixed and lexicographically sortable while remaining unique.
→ Don't use UUIDs as security tokens. UUIDs (especially v1 and v4) are not designed to be unguessable secrets. For authentication tokens, API keys, or password reset links, use a cryptographically secure random generator instead.

Frequently Asked Questions

What is a UUID?

A 128-bit identifier formatted as 32 hex digits (8-4-4-4-12). Designed to be globally unique without a central authority — collision probability is astronomically small.

What is UUID v4?

V4 generates IDs using random numbers — 122 of 128 bits are random. The most commonly used version because it requires no external state or coordination.

UUID vs auto-increment IDs?

Use UUIDs for distributed systems, client-side generation, or when sequential IDs would expose system information. Use auto-increment for simple single-database apps.

What is a UUID?+

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. It's formatted as 32 hexadecimal digits in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs can be generated independently by different systems without coordination and still remain unique.

What is the difference between UUID v1 and v4?+

UUID v1 uses the current timestamp and the machine's MAC address to generate a unique ID — it's sortable by time but can reveal the generating machine's identity. UUID v4 uses random data for all bits (except the version and variant markers), making it the most commonly used version for privacy and simplicity.

Can UUID collisions happen?+

Theoretically yes, practically no. UUID v4 has 2^122 possible values (about 5.3 × 10^36). The probability of generating two identical UUIDs is astronomically low — you'd need to generate a billion UUIDs per second for about 85 years to have a 50% chance of one collision.

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