UUID Bit Layout Explained (RFC 9562)
Every UUID is a 128-bit value divided into named fields defined by RFC 9562 (formerly RFC 4122). The layout differs by version: v7 uses the first 48 bits for a millisecond timestamp; v1 splits a 60-bit Gregorian timestamp across three non-contiguous fields; v4 fills almost everything with random data.
Understanding the bit layout matters when you are debugging ID collisions, verifying sort order, or implementing a UUID generator that must conform to the specification. This tool renders all 128 bits as a color-coded grid — hover any cell to see which field it belongs to, its position within that field, and the full field value in hex and decimal.
The proportional segment bar above the grid gives an at-a-glance picture of how much space each field occupies — useful for comparing how different versions trade randomness for timestamp resolution.
How to use
- Paste one or more UUID strings into the main tool — version is auto-detected.
- Hover any cell in the 128-bit bitfield diagram to see the field name, bit index, and full field value.
- For batch UUIDs, check the monotonic-order badge and timestamp timeline to verify generation order.