UUID Generator
Generate RFC 4122 compliant UUID v4 identifiers instantly. Bulk generate, format options, copy-all in one click.
📋 What is UUID v4?
UUID v4 uses random data to create a 128-bit identifier. Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The "4" and "y" bits are fixed per the RFC 4122 spec.
🎲 Collision Probability
With 2¹²² possible values, the chance of a collision is astronomically small. You'd need to generate a billion UUIDs per second for 85 years to have a 50% collision chance.
🔒 Browser-Side Only
Generated using crypto.randomUUID() (with fallback). Nothing is sent to any server — these are yours alone.
UUID Generator — FAQ
What's the difference between UUID and GUID?
They're the same thing. GUID (Globally Unique Identifier) is Microsoft's term for UUID. Both follow the same RFC 4122 specification and produce identical-format identifiers.
Is UUID v4 suitable for database primary keys?
Yes, but consider UUID v7 for databases — it's time-ordered so it creates less index fragmentation. UUID v4 is ideal for session tokens, API keys, correlation IDs, and any case where unpredictability matters.
Are these UUIDs safe to use in production?
Yes. This tool uses your browser's cryptographically secure random number generator (crypto.randomUUID()), the same source used in production security software.
Should I store UUIDs as text or binary?
Storing as text (a CHAR(36) column) is the simplest approach and works with every database. For large tables, 16-byte binary storage halves the space. PostgreSQL has a native UUID type that stores them compactly and sorts them as numbers, not strings.
Is UUID v4 good enough for API tokens and session IDs?
Yes for most systems. A v4 UUID carries 122 bits of randomness, which is far beyond anything that can be guessed or brute-forced. For the most sensitive secrets, security teams still prefer dedicated random key generators with even more entropy, but a CSPRNG-generated v4 is a solid choice for sessions, API keys, and correlation IDs.
What's the difference between UUID v4 and v7?
UUID v4 is fully random. UUID v7 is time-ordered — the first 48 bits encode a timestamp, the rest is random. When used as database primary keys, v7 values are inserted sequentially, which reduces index fragmentation and page splits under heavy write load.
How to Generate UUIDs
UUIDs are generated locally with your browser's cryptographic random number generator — the same primitive used by production security software — so every value you see is unique to your session and never transmitted anywhere. The generator starts with five fresh UUIDs on load, so you can copy one immediately without touching a button.
- Set the quantity. Use the number input to generate anywhere between 1 and 100 UUIDs at once — useful for seeding test data or wiring up fixtures.
- Pick a format. Standard lowercase with dashes is the convention. Uppercase, no-dashes (32 hex characters), and braces-wrapped formats exist because some systems require them, for example certain Windows APIs and legacy databases.
- Click Generate. New values replace the current list. Formatting changes apply to already-generated values too — switch formats without regenerating.
- Copy what you need. Use the icon on each row for a single UUID, or Copy All to grab the whole list as one line per UUID.
- Regenerate freely. Nothing is stored, tracked, or persisted. Close the tab and every value vanishes.
Where UUIDs Are Used, and Choosing the Right Version
UUIDs have become the default identifier in almost every codebase. They power database primary keys, event and correlation IDs in distributed tracing, idempotency keys, file names for generated assets, and user-facing references in URLs. Because they are generated in an isolated browser tab with no collision coordination, they breathe easy where auto-incrementing counters and single-sequence clusters cannot — no central server is needed.
Choosing a version matters only in databases, where inserting random keys as primary keys causes constant index-page splits and cache misses. In that setup, prefer UUID v7 (time-ordered) so new rows append roughly sequentially. The one version to avoid is v1: it encodes the generating machine's MAC address, which leaks hardware identity and is essentially predictable. For general identifiers, sessions, and any place where unpredictability helps, v4 — what this tool produces — remains the default.
- Identifiers in APIs. Returning UUIDs in JSON (e.g.
{"id":"f47ac10b-58cc-4372-a567-0e02b2c3d479"}) is the de facto format in every major API design guide. - Files and object storage. Named files as UUIDs avoid collisions when users upload, and safer than disclosing sequential or timestamped names.
- Log correlation. A single UUID per request across services makes tracing far easier.