Departures boardRecently wasted
Every identifier below is unique in the universe and will never be used for anything. Tap a row to copy it anyway.
| Time | Plat. | Destination | Identifier | Status |
|---|
Waiting room, left of the ticket officeThe Lava Lounge
Blackjack while you wait for the 14:07 to Vesuvius. Six-deck shoe, double on any two cards. House currency is lava rocks. Wins make the mountain erupt.
End of platform 4, out over the lavaThe Hookers
The Lava-Pier Angling Society has fished spent identifiers out of the magma since 1883. Every UUID you waste drifts downriver; one of the crew hooks it before it sinks for good.
The creel · today's catch
Information deskAbout UUID v4
What the identifiers on the board are, and how to make your own when you are not standing next to a volcano.
What is a UUID v4?
A UUID (universally unique identifier, also called a GUID) is a 128-bit value written as 32 hexadecimal digits in five groups, like 3f2b8c1e-9a4d-4e7f-b2c6-1d0e5a7f9b33. Version 4 fills 122 of those bits with random data. The other 6 bits are fixed: the 4 that opens the third group is the version, and the 8, 9, a or b that opens the fourth group is the RFC 9562 variant. Those are the two digits highlighted on the board.
Can two random UUIDs collide?
In theory yes, in practice no. There are about 5.3 × 10³⁶ possible v4 UUIDs. You would need to generate roughly 2.7 × 10¹⁸ of them before the chance of a single duplicate reaches 50%.
Are the UUIDs generated here private?
Yes. Every UUID is generated in your browser with crypto.randomUUID() from the Web Crypto API. Nothing is sent to a server, and the page keeps only your last few in your own browser's local storage.
How do I generate a UUID v4 in code?
- JavaScript:
crypto.randomUUID() - Python:
str(uuid.uuid4()) - PostgreSQL:
gen_random_uuid() - Linux shell:
cat /proc/sys/kernel/random/uuidoruuidgen -r - Go:
uuid.NewString()fromgithub.com/google/uuid
Is it really a waste?
No. The space is so large that discarding one costs nothing, which is the whole joke of this page.