UUID Generator

Invalid UUID format

Cause: The string is not 8-4-4-4-12 hex characters. Extra whitespace, missing dashes, or non-hex characters break parsers.

Fix: Trim the input and check for exactly 32 hex chars with dashes at positions 8, 12, 16, 20. This tool's Parser auto-strips whitespace and curly braces {} for .NET GUID compatibility.

Unknown UUID version

Cause: The 13th hex character is not in 1-8, so the version field is out of spec.

Fix: Verify the source UUID was generated correctly. Non-standard or corrupted UUIDs may have garbage in the version bits.

Invalid variant bits

Cause: The high 2 bits of the 17th hex char are not 10 (RFC 9562) — e.g., an Apple NSUUID with variant 110 (Microsoft).

Fix: Check the UUID's origin. RFC 9562 variants start with 8, 9, a, or b at that position.

Namespace UUID required

Cause: v3 or v5 selected without a namespace UUID and name.

Fix: Choose a standard namespace (DNS, URL, OID, X.500) or provide a valid custom UUID, then enter a name string.

Alphabet contains duplicates (NanoID)

Cause: Custom NanoID alphabet has repeated characters, which skews distribution.

Fix: Provide an alphabet with all unique characters. The tool rejects duplicates before generation.

Is UUID v7 secure enough for session tokens?

No. UUID v7 embeds a Unix millisecond timestamp in the first 48 bits, which is predictable. For session tokens, API keys, or anything requiring unpredictability, use UUID v4 (fully random) or a dedicated CSPRNG-backed token.

What happened to UUID v2?

UUID v2 (DCE Security) is defined in the original spec but rarely used. Most modern libraries (Python uuid, Java UUID, Go google/uuid) do not implement it. This tool recognizes v2 in the Parser for debugging but does not generate v2 — it is essentially legacy.

Why did PostgreSQL 18 add uuidv7()?

UUID v7 is time-ordered, making it a much better primary key than v4. PostgreSQL 18 (released September 2025) added a native uuidv7() function because benchmarks consistently show 2-10x better INSERT performance with v7 due to sequential index writes.

Can I sort UUID v4 by creation time?

No. UUID v4 is fully random and has no time component. If you need time-ordered identifiers, use UUID v7, UUID v6, or ULID. These all embed a timestamp that makes them lexicographically sortable by creation time.

Is ULID better than UUID v7?

They solve the same problem (time-ordered IDs) but differ in format. ULID is 26 characters in Crockford Base32, more compact than UUID's 36 characters with dashes. UUID v7 is the RFC-standardized option with broader tooling support. Choose ULID for compactness, v7 for standards alignment.

How unique is NanoID compared to UUID?

Default NanoID (21 chars from a 64-char alphabet) has collision probability equivalent to UUID v4 — you would need ~149 quadrillion IDs to hit a 1% collision rate. Shorter NanoIDs are less unique; an 8-char ID from a 36-char alphabet hits 1% collision at ~370K IDs.

Can UUIDs collide?

In theory yes, but for UUID v4 the probability is astronomically small — about 1 in 2^122 for any two specific UUIDs. You would need to generate about 2.7 quintillion UUIDs to reach a 50% chance of collision. In practice, treat them as globally unique.

Are UUIDs really universally unique?

The "universally unique" guarantee comes from the 128-bit length and cryptographically strong randomness (v4) or timestamp + randomness (v7). As long as you use a proper CSPRNG, collision across the entire universe of generated UUIDs is negligibly small.

Is it safe to paste UUIDs here?

Yes. All processing happens entirely in your browser using JavaScript. Your data is never sent to any server. You can verify this by opening the Network tab in your browser's developer tools — no network requests are made after the page loads.

Why does Node.js crypto.randomUUID() only support v4?

crypto.randomUUID() is a standardized Web Crypto API method that specifically returns a v4 (random) UUID. For v7 and other versions, you need an external library like uuid on npm. Python's uuid module similarly defaults to v4 and added uuid7() only in Python 3.14.