🔑 UUID Generator
Generate cryptographically random UUID v4 or timestamp-based UUID v1 identifiers — single or bulk up to 1000, with format options. Free, instant, browser-only.
✅ Validate a UUID
📚 What Is a UUID?
A UUID (Universally Unique Identifier), standardized in RFC 9562, is a 128-bit value written as 32 hexadecimal digits grouped into five sections separated by hyphens: 8-4-4-4-12 characters, e.g. 550e8400-e29b-41d4-a716-446655440000. Its purpose is to be unique across systems, servers, and time without requiring any central registry or coordination — any two independently generated UUID v4s are, for all practical purposes, guaranteed never to collide.
🔢 UUID Versions Explained
| Version | Based On | Sortable? | Common Use |
|---|---|---|---|
| v1 | Timestamp + node/MAC identifier | Yes, chronological | Systems needing creation-order tracking |
| v4 | Cryptographically random bits | No | Database keys, API tokens, session IDs — most common choice |
| v5 | SHA-1 hash of a namespace + name | No, deterministic | Generating the same UUID reproducibly from the same input |
| v7 | Unix timestamp + random bits | Yes, chronological | Modern choice combining sortability with randomness |
This tool generates v4 (the most widely used, fully random) and v1 (timestamp-based). Read the full breakdown in our guide: UUID vs GUID Explained.
🔑 Why UUIDs Instead of Auto-Increment IDs?
- No central coordination needed: Multiple servers or services can generate IDs independently without ever needing to check with each other to avoid collisions.
- Harder to enumerate: Sequential IDs (1, 2, 3…) let anyone guess adjacent records exist. Random UUIDs give no such hint.
- Safe for merging datasets: Combining records from multiple databases without ID collisions is trivial with UUIDs, painful with auto-increment integers.
- Works offline: A client can generate a valid, permanent ID before ever syncing with a server.
⚠️ Tradeoffs to Know
Storage Size
A UUID takes 16 bytes versus 4-8 bytes for an integer — meaningful at very large scale across many indexed rows.
Index Locality
Random UUID v4 as a primary key can fragment B-tree indexes since inserts land in random positions rather than appending sequentially.
Human Readability
Nobody can read a UUID out loud accurately or remember one — fine for machine use, poor for anything user-facing.
Mitigation: UUID v7
Newer UUID v7 embeds a timestamp prefix, restoring index-friendly sequential ordering while keeping the rest random.
🛠️ Use Cases
Database Primary Keys
Especially useful in distributed or sharded databases where independent ID generation matters more than sequential ordering.
API Keys & Session Tokens
A random, unguessable identifier is exactly what's needed for session tokens, API keys, and request-tracing IDs.
File & Object Naming
Uploaded file storage systems commonly use UUIDs as filenames to guarantee no collision regardless of the original filename.
Test Data Generation
Generate bulk UUIDs quickly to populate test fixtures, mock datasets, or seed scripts during development.
🔗 More Developer Tools
Convert timestamps with our Unix Timestamp Converter, or generate secure passwords with our Password Generator. Read the full guide: UUID vs GUID Explained.
FAQ
What is a UUID? +
A 128-bit value (RFC 9562) written as 32 hex digits in five hyphen-separated groups, designed to be unique across systems without central coordination.
What is the difference between UUID v1 and v4? +
v1 derives from timestamp plus a node identifier, making it sortable but potentially revealing generation time. v4 is fully random, offering no ordering but stronger privacy.
How unique is a UUID v4, really? +
With 122 random bits, the collision probability among a billion UUID v4s remains astronomically small — for practical purposes they're treated as guaranteed unique.
Are UUIDs generated by this tool cryptographically secure? +
Yes — it uses crypto.getRandomValues(), a cryptographically secure random source, not Math.random().
Can I use a UUID as a database primary key? +
Yes, common especially in distributed systems. The tradeoff is larger storage (16 bytes) and potentially worse index locality versus sequential integers.
What does a nil UUID mean? +
00000000-0000-0000-0000-000000000000 — a reserved special value meaning "no UUID" or an unset identifier.
Is this UUID generator free with no limits? +
Yes — unlimited generation, individually or in bulk up to 1000 at a time, no sign-up, no rate limiting.
What is a GUID and is it different from a UUID? +
GUID (Globally Unique Identifier) is Microsoft's term for the same underlying concept — functionally equivalent to a UUID in virtually all practical contexts.
Can two different systems generate the same UUID v4 by coincidence? +
Theoretically possible but practically negligible — you'd need to generate roughly a trillion UUIDs before a 50% chance of even one collision.
Why does my UUID have specific characters like "4" and "a" in fixed positions? +
Those positions encode the UUID version and variant per the RFC 9562 spec — the "4" marks it as version 4, and the variant bits are constrained to specific values.
Is UUID v1 a privacy risk? +
It can be, since it embeds a timestamp and originally a MAC address (modern implementations use random node IDs instead) — v4 is generally preferred when no ordering is needed.
What is UUID v7 and should I use it instead? +
v7 embeds a Unix timestamp prefix followed by random bits, giving both chronological sortability and strong randomness — increasingly preferred for new systems needing both properties.
Can I generate UUIDs in bulk for testing? +
Yes — set the count field up to 1000 and download as .txt or .csv for use in test fixtures or seed scripts.
Do UUIDs expire or become invalid? +
No — a UUID is a permanent, static value with no built-in expiry. Any expiration logic must be implemented separately by your application.
Which UUID version should I use by default? +
Version 4 (random) is the safe default for most use cases — API keys, session tokens, general-purpose IDs. Reach for v1 or v7 specifically when you need chronological sortability.