UUID Generator
Generate random UUID v4 identifiers. Generate single or bulk UUIDs with one click.
Reviewed May 25, 2026. Privacy model: tool input is processed in your browser and is not uploaded to BytePane servers.
About UUID Generator
UUIDs (Universally Unique Identifiers) are 128-bit numbers used to uniquely identify resources in distributed systems without requiring a central authority. They are standardized by RFC 4122 and are the preferred identifier format for database primary keys, API request tracking, session management, and distributed system coordination. UUID v4 is the most widely used version, generating identifiers from cryptographically secure random numbers with a collision probability so low that generating 1 billion UUIDs per second for 86 years would still yield only a 50% chance of a single duplicate.
UUID Versions Quick Reference
UUID v1 uses the current timestamp and MAC address, making it time-sortable but potentially exposing hardware information. UUID v3 and v5 generate deterministic IDs from a namespace and name using MD5 and SHA-1 hashing respectively. UUID v4 is purely random and the most commonly used for general-purpose unique identification. UUID v7, introduced in the 2024 update to RFC 9562, combines a Unix timestamp with random bits, providing both uniqueness and natural chronological sorting -- making it ideal for database primary keys where index performance matters.
The UUID format is xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M indicates the version (4 for v4) and N indicates the variant (8, 9, a, or b for RFC 4122). UUIDs can be represented with or without dashes and in uppercase or lowercase. When used as database primary keys, consider UUID v7 or ULID for better index locality compared to random UUID v4. Popular alternatives to UUID include ULID (26-character, Crockford Base32), nanoid (URL-safe, customizable length), and KSUID (K-Sortable Unique ID).
When UUID v4 is the right choice
UUID v4 is a good fit for public API IDs, request IDs, correlation IDs, distributed job IDs, idempotency keys, fixture data, and browser-side identifiers where the client should not ask a central server for the next number. For high-write database tables, random v4 keys can still be valid, but UUID v7, ULID, or a separate sortable surrogate key may reduce index churn.
API and event IDs
Random UUIDs avoid leaking user count, sequence, or creation rate.
Distributed systems
Separate services can create IDs without coordination.
Database tradeoff
For very large ordered indexes, compare UUID v4 with UUID v7 or ULID.
Frequently Asked Questions
What is a UUID?
UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. UUIDs are standardized by RFC 4122 and are commonly used as database primary keys, session tokens, and unique identifiers in distributed systems.
What is UUID v4?
UUID version 4 is generated using random or pseudo-random numbers. It has the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hex digit and y is one of 8, 9, a, or b. The "4" in the third group indicates version 4.
Does BytePane use cryptographically secure UUID generation?
Modern browsers use Web Crypto for crypto.randomUUID(). If randomUUID is unavailable, BytePane uses crypto.getRandomValues() and sets the UUID v4 version and variant bits manually.
Should I use UUID v4 or UUID v7 for database primary keys?
Use UUID v4 when you need simple random identifiers and do not care about insertion order. Use UUID v7 or ULID when database index locality and chronological sorting matter, because random v4 values can fragment B-tree indexes at high write volume.
Can two UUIDs be the same?
Theoretically yes, but practically no. There are 2^122 possible UUID v4 values (about 5.3 x 10^36). The probability of generating duplicate UUIDs is astronomically low — you would need to generate 1 billion UUIDs per second for 86 years to have a 50% chance of a collision.