UUID Generator Online — Free UUID v4, v7, ULID, Nano ID Generator

How to UUID Generator Online

1. 1

   Select the ID format: UUID, ULID, Nano ID, or CUID2.

2. 2

   For UUIDs, choose the version: v1 (timestamp+MAC), v4 (random), v6 (reordered timestamp), or v7 (Unix timestamp + random).

3. 3

   Set the output format: standard (lowercase with dashes), uppercase, no dashes, braces, URN, or Base64.

4. 4

   Set the count (1–500) for bulk generation. Click Generate or press ⌘↵.

5. 5

   Copy individual IDs with the per-row copy button, or copy all at once with ⌘⇧C.

6. 6

   To validate or decode a UUID, switch to Validate or Decode mode and paste your UUID.

UUID Generator Features

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  UUID v1, v4, v6, v7 generation per RFC 9562

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  Nil UUID (all zeros) and Max UUID (all ones) constants

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  ULID generation: Universally Unique Lexicographically Sortable Identifier (millisecond timestamp + 80-bit random)

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  Nano ID generation: compact, URL-friendly, configurable length (10–64 characters)

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  CUID2 generation: collision-resistant IDs optimized for horizontal scaling

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  Bulk generation: create up to 500 IDs at once in a single click

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  6 output formats: standard, uppercase, no-dashes, braces {…}, URN urn:uuid:…, Base64

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  UUID validation: checks format, version, and variant compliance per RFC 9562

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  UUID decoding: extracts timestamp, version, variant, clock sequence, and node from v1/v6/v7

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  ID format auto-detection: recognizes UUID, ULID, and Nano ID from pasted input

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  Per-row copy buttons for easy copying in bulk mode

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  Version comparison table: side-by-side comparison of entropy, sortability, and URL-safety

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  URL-shareable settings: configuration persisted in URL parameters

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  Works entirely in your browser — no data is ever sent to a server

Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier standardized by RFC 9562. It is expressed as a hex string in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be unique across distributed systems without a central authority — the probability of generating two identical UUIDs is astronomically low.

What is the difference between UUID v4 and v7?

UUID v4 is entirely random (122 bits of randomness) — it provides excellent uniqueness but cannot be sorted chronologically. UUID v7 encodes the current Unix timestamp in milliseconds in the first 48 bits, followed by 74 bits of randomness. This makes v7 time-sortable, which is ideal for database primary keys because new rows always sort after older ones, improving index performance.

What is a ULID?

A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier encoded in 26-character Crockford Base32. The first 10 characters encode the current timestamp in milliseconds; the remaining 16 are random. ULIDs are lexicographically sortable, URL-safe, and compatible with UUID storage columns when converted.

What is a Nano ID?

Nano ID is a small, URL-safe, cryptographically random ID generator. The default 21-character Nano ID using a 64-character alphabet provides approximately 126 bits of randomness — comparable to UUID v4. It is more compact than UUIDs, URL-safe by default, and popular in JavaScript applications as a lighter alternative to uuid.

What is CUID2?

CUID2 (Collision-Resistant Unique Identifier v2) is designed for horizontal scaling and distributed systems. It includes a timestamp, a fingerprint derived from the host environment, and cryptographically random data. CUID2 is more resistant to collision under high concurrency than UUID v4 and is URL-safe.

Which UUID version should I use?

For database primary keys, prefer UUID v7 (time-sortable, better index performance) or CUID2. For general random IDs, use UUID v4. For URL-friendly short IDs, use Nano ID. For time-sortable but more compact IDs, use ULID. For legacy systems that expect MAC-based UUIDs, use UUID v1. UUID v6 is a reordered v1 that is more database-friendly.

Is UUID v4 truly random?

UUID v4 fills 122 of its 128 bits with cryptographically random data (the other 6 bits are fixed for version and variant). This represents 2^122 ≈ 5.3 × 10^36 possible values. The probability of generating a duplicate is approximately 50% only after generating 2.71 × 10^18 (2.71 quintillion) UUIDs — effectively zero for any realistic use case.

Can UUID v7 replace auto-incrementing IDs?

Yes, UUID v7 is designed as a direct replacement for auto-incrementing integer primary keys in distributed systems. Because it encodes the current timestamp in the leading bits, it maintains the insertion-order property that makes integer IDs database-friendly, while providing globally unique values without a central sequence generator.

Are UUIDs case-sensitive?

No. UUIDs are defined as case-insensitive per RFC 9562. Both f47ac10b-58cc-4372-a567-0e02b2c3d479 and F47AC10B-58CC-4372-A567-0E02B2C3D479 represent the same UUID. The standard representation uses lowercase. This tool validates UUIDs regardless of case and normalizes output to lowercase by default.

How many UUIDs before a collision?

For UUID v4: you would need to generate approximately 2.71 × 10^18 (2.71 quintillion) UUIDs to reach a 50% chance of collision. In practice, a system generating 1 million UUIDs per second would take over 85 years to reach this probability. For ULID and UUID v7, the millisecond prefix further reduces practical collision probability within a single process.

Is this UUID generator free?

Yes, completely free with no usage limits. All generation, validation, and decoding runs directly in your browser — no account required.

Is my data safe?

All processing happens entirely in your browser using JavaScript. No IDs, inputs, or settings are ever transmitted to a server or stored anywhere outside your browser. Your data stays completely private.

Does it work offline?

Yes. All logic is bundled with the page as pure JavaScript. Once the page has loaded, the UUID Generator works without an internet connection.

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