UUID Generator
Generate Universally Unique Identifiers (UUIDs) in v1, v4, and v5 formats instantly. UUIDs are 128-bit identifiers guaranteed to be unique across all systems and time without a central registry. Used as primary keys, API request IDs, session tokens, and file names. Generated in-browser using the Web Crypto API — nothing is sent to a server.
UUID Generator
Bulk Generation
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The standard (RFC 4122) defines a format of 32 hexadecimal digits in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
The probability of generating two identical UUIDs is so astronomically small (1 in 2¹²²) that collisions are considered impossible in practice, making them ideal for distributed systems where unique IDs are needed without coordination.
UUID Versions Explained
v1 — Time-based
Uses MAC address + timestamp. Sequential IDs, but leaks hardware information.
v4 — Random (most common)
Cryptographically random. No pattern or ordering. Best for most applications.
v5 — Namespace + SHA-1
Deterministic — same namespace + name always produces the same UUID.
Tips & Tricks
- Use v4 for most cases — it is random and does not leak any system info
- Use v5 for deterministic IDs (same input always produces same UUID)
- Avoid v1 in public-facing apps — it exposes your MAC address
- Store in databases as BINARY(16) not VARCHAR(36) to save space
- UUID is case-insensitive — both upper and lowercase are valid
Common UUID Use Cases
Database Keys
Primary keys that do not expose sequential record information to users.
Distributed IDs
Generate IDs across multiple servers/nodes without coordination.
Request Tracing
Unique IDs for API requests and events in distributed tracing systems.
File Names
Conflict-free, unique file names for uploads and stored assets.
Frequently Asked Questions
Related Tools
UUIDs in Distributed Systems and Modern Architecture
Universally Unique Identifiers solve one of the fundamental challenges of distributed computing: generating globally unique identifiers without a central authority. In microservices, event-driven architectures, and multi-region deployments, multiple systems must generate IDs simultaneously without coordination. UUIDs provide a 128-bit identifier with an astronomically low collision probability (1 in 2¹²² for v4) that makes coordination unnecessary — the standard choice for database primary keys, API request tracing, session tokens, and event sourcing systems.
Choosing the Right UUID Version
UUID v4 (random) is the best default choice — 122 bits of cryptographic randomness with no pattern and no information leakage. UUID v1 (time-based) embeds a timestamp and MAC address, creating sequential IDs efficient for indexing but exposing hardware information. UUID v5 (namespace + SHA-1) is deterministic: the same namespace and name always produce the same UUID, ideal for idempotent operations and content addressing. For newer projects, consider UUID v7 which combines timestamp-based ordering with random bits — giving you indexing efficiency with privacy.
Database Storage and Performance
Storing UUIDs as VARCHAR(36) wastes 20 bytes per row compared to BINARY(16) or a native UUID type. PostgreSQL has a built-in uuid type that stores efficiently and supports indexing natively. Random UUIDs (v4) cause B-tree index fragmentation — if write performance matters, consider ordered UUIDs like ULID or UUID v7. For securing your application, generate strong credentials with the Password Generator, inspect tokens with the JWT Decoder, and encode data with the Base64 Tool. Debug APIs using the API Request Builder. Explore all tools on the homepage.