Generate Random UUIDs — v4, Bulk, Copy Instantly

What This Tool Does

This generator creates UUID v4 identifiers using your browser’s Web Crypto API. Single generation, bulk output (up to 1,000 at once), and clipboard export are all supported. Output can be formatted as standard hyphenated UUIDs, no-hyphen strings, or uppercase variants.

How It Works

UUID v4 structure is defined by RFC 4122:

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

• 32 hex digits arranged in 5 groups separated by hyphens
• Group lengths: 8-4-4-4-12
• Bit 6–7 of the third group is fixed to 0100 (version 4)
• Bit 6–7 of the fourth group is fixed to 10xx (variant 1)
• All other 122 bits are cryptographically random

The tool calls crypto.randomUUID() natively where supported (all modern browsers), with a crypto.getRandomValues() fallback for older environments.

What Are Common Use Cases?

Database primary keys. UUID primary keys are standard in microservices architectures where multiple services create records independently. Unlike auto-increment integers, UUIDs don’t require a centralized sequence and don’t expose record counts to clients.

API tokens and session IDs. A UUID v4 provides sufficient randomness for a session identifier or one-time token in contexts where a formal cryptographic token (like a signed JWT) is not needed.

File naming for uploads. When users upload files, storing them with their original names risks collisions and path traversal attacks. Rename each file to a UUID on upload: a3f2c910-7bde-4d6a-b3e1-9f405c2b871a.jpg.

Idempotency keys. APIs like Stripe require an idempotency key per request to prevent duplicate charges if a network retry occurs. Generate a fresh UUID for each request and store it locally before sending.

Feature flag and experiment IDs. A/B testing and feature flag systems assign users to cohorts using stable IDs. If no user ID exists (anonymous visitor), generate a UUID, store it in localStorage, and use it consistently for the session lifetime.

Synthetic test data. When seeding a test database with realistic-looking records, generate UUIDs for ID columns instead of sequential integers. This more accurately reflects production data distribution for index performance testing.

How Do UUID Versions Compare?

Version	Source	Sortable	Privacy-Safe	Common Use
v1	Timestamp + MAC address	Yes	No	Legacy systems
v3	MD5 hash of namespace + name	Deterministic	N/A	Namespace-based IDs
v4	Random	No	Yes	Most applications
v5	SHA-1 hash of namespace + name	Deterministic	N/A	Namespace-based IDs
v7	Timestamp + random	Yes	Yes	DB primary keys (modern)

UUID v4 is the right choice when you need a guaranteed-unique, opaque, privacy-safe identifier and sort order does not matter.

What Output Format Options Are Available?

Format	Example
Standard (hyphenated)	550e8400-e29b-41d4-a716-446655440000
No hyphens	550e8400e29b41d4a716446655440000
Uppercase	550E8400-E29B-41D4-A716-446655440000
Braces (Windows GUID)	{550e8400-e29b-41d4-a716-446655440000}
URN	urn:uuid:550e8400-e29b-41d4-a716-446655440000

Frequently Asked Questions

Are the UUIDs generated here truly random? Yes. The Web Crypto API derives randomness from the operating system’s entropy pool — hardware events, CPU timing jitter, and similar sources. This is the same CSPRNG used for HTTPS and password hashing. The output is not predictable.

Do I need to check for duplicates before using a UUID? In practice, no. The collision probability for UUID v4 is lower than the probability of hardware failure causing a silent data corruption. Applications generating billions of UUIDs per year still have negligible collision risk. Checking for duplicates is a reasonable database constraint to have, but it should never trigger in practice.

Can I use UUIDs generated in the browser for security-sensitive tokens? For low-to-medium sensitivity (session cookies, idempotency keys), yes. For high-security tokens (password reset links, API keys), prefer a purpose-built token library that additionally includes a HMAC signature or KDF-derived secret, rather than a raw UUID.