Create a version 4 UUID in your browser. A reproducible seed is optional and is not a secret.
Each identifier uses the 8-4-4-4-12 hexadecimal shape of a version 4 UUID. By default the browser randomUUID function supplies it. The value is not written into the page address.
Generate calls the browser randomUUID function. The result has the version 4 nibble and the variant bits from the UUID rules. You can ask for up to 20 identifiers at once. They are created locally.
Reproducible mode is a separate choice and stays off until you check it. It hashes a seed into the same identifier shape. Anyone who can see the seed can rebuild those identifiers, so do not treat them as unguessable.
Choose how many identifiers you need.
Press Generate. They are created in this browser and are not added to the address.
Check reproducible mode only when a fixture must stay the same across reloads.
The value uses the version 4 shape. A later visit creates a different identifier unless you opted into a seed.
Publishing a reproducible page address and then treating the identifier as unguessable.
Yes, unless reproducible mode is on. A normal refresh asks the browser for new identifiers.
No. Anyone with the seed can rebuild it. Use the default generator when the value must stay unguessable.