What is the difference between UUID v4 and v7?

UUID v4 is fully random. UUID v7 embeds a Unix timestamp in the first 48 bits, making IDs sortable by creation time while remaining unique.

ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that is timestamp-ordered and encoded in Crockford's Base32, making it more compact than UUID strings.

Are the generated IDs truly random?

Yes. We use the Web Crypto API (crypto.getRandomValues) which provides cryptographically secure random numbers.

Which UUID version should I use?

Use UUID v4 (random) for most use cases — it's simple and collision probability is negligible. Use UUID v7 when you need time-sortable IDs (e.g., database primary keys where insert order matters). Use ULID if you need a shorter, URL-friendly, sortable format.

Can UUIDs collide (generate duplicates)?

In practice, no. UUID v4 has 122 random bits, producing 5.3×10³⁶ possible values. The probability of generating a duplicate is astronomically low — you'd need to generate 2.7 quintillion UUIDs to have a 50% chance of one collision.

Can I generate UUIDs in bulk?

Yes. Generate up to 1,000 UUIDs at once. Copy them individually or as a full list in various formats (one per line, comma-separated, JSON array, or SQL values).

UUID Generator — v4, v7, ULID & NanoID Online

How to Use the UUID / ULID Generator

Select your preferred ID type (UUID v4, UUID v7, or ULID), set the count (up to 1,000), and click generate. Each ID can be copied individually or use "Copy All" to grab the full list. Enable uppercase for a consistent visual style. IDs are generated using the Web Crypto API for cryptographic randomness.

What Is the Difference Between UUID v4, v7, and ULID?

UUID v4 is the most common type — it is fully random with 122 bits of entropy, giving a collision probability so low it is effectively zero. UUID v7 embeds a Unix timestamp in the first 48 bits, making IDs naturally sortable by creation time while retaining randomness. Use our Timestamp Converter to inspect the embedded timestamps. This makes v7 ideal for database primary keys where insertion order matters for performance. ULID is an alternative format that is also timestamp-ordered but uses Crockford Base32 encoding, producing shorter, more compact strings than standard UUID format.

Common Use Cases

Generate unique identifiers for database records, API resources, or distributed systems. Create correlation IDs for request tracing across microservices. Generate session tokens, idempotency keys, or secure API tokens with our Password Generator. For cryptographic hashing of your identifiers, try our Hash Generator. Bulk generate test data IDs for development and staging environments. UUID v7 is recommended for new projects using SQL databases, as timestamp-ordered keys improve B-tree index performance compared to fully random v4 UUIDs.

UUID / ULID Generator

How to Use the UUID / ULID Generator

What Is the Difference Between UUID v4, v7, and ULID?

Common Use Cases

Frequently Asked Questions

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