UUID Generator

What the UUID Generator does

UUID Generator: generates Status and UUIDs from How many?. Example: how many? 5 gives status Generated 5 UUID(s).

Give the UUID Generator your How many? and it works out Status and UUIDs. Everything recomputes live, which makes it easy to test a few scenarios in a row.

Pasting a production payload into an unknown web tool is a real risk, which is why this one stays local. The UUID Generator exists to take that particular chore off your hands.

Nothing is uploaded: useful when the text you are inspecting contains keys or customer records.

The field table, the method and a worked example are documented after the tool for anyone who wants to check the working.

What do the UUID Generator fields mean?

The UUID Generator uses 1 input. It opens with a complete example loaded, which is usually the quickest way to understand what a field means.

How does the UUID Generator work?

Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same generated output.

Each field is verified before use; failures are reported explicitly rather than swallowed.

Worked example

These are the values the UUID Generator loads by default, and the result it produces from them. The numbers below come straight from the default inputs, so you can verify them against the live tool.

Using UUIDs in a real schema

Generating a UUID is the easy part. The decisions that actually cost you later are how you store it, whether you index it, and whether its randomness fights your database. A v4 UUID is 128 bits: 36 characters as canonical text, 16 bytes as binary.

Worth knowing

• A random v4 makes a poor clustered primary key. Because consecutive inserts land at random points in the B-tree rather than at the end, the index suffers page splits and loses the cache locality that a sequential key gives you for free. This is a well-known cost in clustered-index engines such as InnoDB, and it grows with table size.
• RFC 9562 (May 2024) added version 7, a time-ordered UUID that puts a millisecond timestamp in the high bits, and obsoleted the older RFC 4122. v7 is the modern answer when you want UUID-style uniqueness without giving up insert locality. This tool generates v4, which is still the right pick when the identifier must leak nothing about creation time.
• In the browser, crypto.randomUUID() is only available in a secure context: HTTPS or localhost. On a plain http:// page it is undefined, which is a common cause of "randomUUID is not a function" in staging environments.
• Store the value in a real UUID column where your database has one (PostgreSQL), or BINARY(16) where it does not, rather than CHAR(36). The text form more than doubles the storage and inflates every secondary index that carries the key.
• A UUID is not a good public-facing identifier just because it is unguessable. Thirty-six characters in a URL is a poor experience, and unguessable is not the same as access-controlled: an endpoint still needs authorisation, not just an obscure id.

Sources: RFC 9562: UUID formats · MDN: crypto.randomUUID()

How to use it

1. Set How many? (1 to 50).
2. Results update continuously rather than on submit.
3. Check Status and UUIDs on the right.
4. To keep the result, either copy the link or print the page. Both preserve what is on screen.

What this tool does not do

• Processing happens in your browser, so extremely large inputs are bounded by available memory.
• Output follows the common convention for this format; a specific toolchain may have its own house style.
• The tool answers exactly the question it is given; it cannot know the context around your numbers.
• The tool trusts your numbers completely, so a mis-keyed digit propagates straight through.

Frequently asked questions

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