Developer & Tech

UUID v4 Generator

What this does

Generate one to fifty random UUID version-4 identifiers using crypto.randomUUID with a documented RFC 4122 fallback.

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Calculator inputs

How to use it

Using the uuid v4 generator

  1. 01

    Set the count

    Anywhere from one test fixture to a bulk list of fifty.

  2. 02

    Choose letter case

    Databases rarely care; some legacy systems insist on uppercase.

  3. 03

    Copy from the results panel

    The newline-separated list pastes cleanly into seeds, fixtures or .env files.

Good to know

Why v4 dominates

Time-based UUIDs leak creation order and machine identity; v4 offers neither, just 122 bits of raw randomness. Collision probability across trillions of IDs stays negligible, which is why v4 is the default for primary keys, request IDs and idempotency keys.

Reading the format

  • Third group’s first hex digit: version; always 4 here
  • First hex of the fourth group: variant 10xx; always 8, 9, a or b
  • Everything else: uniformly random hex

How it's calculated

The math behind this calculator

122 random bits → hex 8-4-4-4-12 with version nibble 4 and variant bits 10xx

Each identifier draws randomness from crypto.randomUUID() where the platform provides it, falling back to sixteen cryptographically-filled bytes with the RFC 4122 version-4 and variant bits set manually; identical guarantees either way.

The batch is checked internally for duplicates as a sanity signal. Generation happens at runtime, so the primary summary stays deterministic while the fresh UUIDs appear in the rows below, ready to copy.

Assumptions & limitations

  • Randomness comes from the platform CSPRNG (or Math.random fallback in insecure contexts).
  • Version field fixed at 4; variant fixed at RFC 4122 (10xx).
  • Batches capped at 50 per run.

Worked example

Requesting five identifiers yields a lowercase batch; each matching the canonical pattern xxxxxxxx-xxxx-4xxx-[89ab]xxx-xxxxxxxxxxxx.

FAQ

Frequently asked questions

Are these cryptographically secure?
Yes; crypto.randomUUID() uses the platform CSPRNG. In non-secure contexts the documented Math.random fallback degrades gracefully but is weaker.
Can I use them as database primary keys?
You can, though fully random IDs hurt B-tree locality versus sequential keys. Many teams adopt ULID-style sortable schemes for large tables instead.
Could two generated UUIDs ever collide?
Theoretically yes, practically no: generating a billion UUIDs per second for a century still leaves collision odds vanishingly small.
Is a UUID the same as a GUID?
Effectively yes; Microsoft’s GUID term refers to the same 128-bit identifier family; the v4 layout is universal today.

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