Define the 122 bits that belong to your application. Mix fixed values, secure randomness, a timestamp, or a counter, and watch the UUID change as you edit. Copy it, or generate a batch of up to 1,000.
xxxxxxxx-xxxx-8xxx-xxxx-xxxxxxxxxxxx
Grey digits are reserved. The 8 marks version 8. The digit after the third hyphen is always 8, 9, a, or b, because it holds the two variant bits and the top two bits of Custom C.
48 fresh random bits in every UUID.
12 fresh random bits in every UUID.
62 fresh random bits in every UUID.
All 122 payload bits are random. That is as much randomness as a UUID v4.
Your batch appears here, ready to copy or download as text, JSON, CSV, or SQL.
The version and variant identify a value as UUID v8. The meaning of its remaining bits belongs to the application that created it. A valid v8 value does not necessarily match another system’s custom layout.
Document the layout you choose. For everyday random IDs, use the UUID v4 generator. For time-ordered IDs, use the UUID v7 generator.
Format reference: RFC 9562, section 5.8.
UUID v8 is the custom UUID format defined in RFC 9562. It reserves four bits for version 8 and two bits for the UUID variant, leaving 122 bits for an application-specific payload.
Choose secure random or fixed hexadecimal values for each custom field. Custom A also supports a Unix millisecond timestamp, and Custom C supports a counter. The page generates locally in your browser and always sets the required version and variant bits.
Use UUID v4 when you simply need random UUIDs. UUID v8 is intended for custom formats. Choose and document your field meanings so the systems reading your UUIDs agree on the layout.
There is no standard UUID v8 timestamp field. This builder optionally stores Unix milliseconds in Custom A, sampling the current time once per batch or using a supplied value. This is a custom layout; use UUID v7 for the standard timestamp format. Ordering within a millisecond depends on the remaining fields.
No. Fixed values repeat, and timestamps can be shared by multiple IDs. A counter creates distinct values within a batch, but restarts from the supplied start value on every generation. Random fields reduce collision risk according to their bit count. Coordinate counters and use a unique constraint where uniqueness matters.
The custom builder runs in your browser. The existing /api/uuid/v8/[count] endpoint and the general bulk UUID generator still generate fully random v8 payloads. Custom settings on this page do not change those tools.