UUID Generator
Generated locally — no data sent to servers.
- Choose the version: v4, v1 or v7.
- Set the quantity.
- Generate and copy one at a time, or use "copy all".
v4 is fully random and the default choice when the identifier should reveal nothing. It is generated here by crypto.randomUUID, the native browser API, with cryptographic randomness.
v7 starts with a millisecond timestamp and fills the rest with random bits. That makes identifiers sort in creation order over time, the property that fixes the main weakness of v4 as a primary key.
v1 is also time-based, but in the older layout, with timestamp fields out of order and a node field that, in the original specification, exposed the machine MAC address. Here that field is random. Use it only for compatibility with legacy systems.
B-tree indexes, used by PostgreSQL and MySQL, work best when inserts land at the end of the tree. Random keys such as v4 fall in scattered positions, fragmenting the index and increasing disk writes.
Because v7 is time-ordered, each new row lands near the previous one. The index grows sequentially, fragmentation drops, and insert performance on large tables improves noticeably.
The trade-off is that v7 reveals when a record was created. If the identifier is public and that information is sensitive, prefer v4.
A UUID has 128 bits, of which 122 are random in v4. The collision probability is negligible in practice, which is why it is safe to generate on different machines with no central coordination.
The canonical format is 36 characters: 32 hexadecimal digits in five hyphen-separated groups. Databases storing them as 16-byte binary save space and gain performance over storing them as text.
Generation happens entirely in your browser; no identifier is transmitted.
Frequently asked questions
In theory yes, in practice no. With 122 random bits in v4, you would need to generate billions per second for decades before a collision stopped being negligible.
UUIDs are preferable when records originate in different places, when the identifier appears in a public URL, or when exposing record order and volume is undesirable. Sequential IDs are still smaller and faster. v7 narrows that gap considerably.
Because the original specification embedded the generating machine MAC address, leaking infrastructure information. This tool uses a random node, but the format remains legacy. v7 serves the same time-ordering purpose with a better design.
The v4 generated by crypto.randomUUID uses cryptographic randomness, so it is unpredictable. Even so, sessions and password resets should use a dedicated token with expiry and revocation, not a reused identifier.
No. Everything is generated in your browser and nothing is logged.