BIP 323: 24 version bits for miners
More of the block header becomes nonce space ASICs can roll on their own.
A small change in the block header that matters to every ASIC: more of the version field becomes nonce space the chip can roll itself.
The change
The 32-bit nonce runs out in a fraction of a second on a modern ASIC, so miners also vary other header fields. BIP 320 (2018) set aside 16 bits of nVersion for that. BIP 323 widens it to 24 bits, bits 5 to 28 (mask 0x1fffffe0), and removes them from BIP 8 and BIP 9 signalling. Nodes apply the mask 0xe000001f when reading soft-fork signals.
Why now
According to the BIP, some devices had begun using 7 bits of nTime as extra nonce, rolling the timestamp more than once a second. Rolling version bits instead keeps block times honest and keeps ASIC controllers from being the bottleneck.
| BIP | Title | Status | Assigned | Replaces |
|---|---|---|---|---|
| 323 | 24 nVersion bits for general purpose use | Draft | 2026-04-22 | BIP 320 |
See every header change miners have lived through on BIPs for miners, and live network numbers on hashrate today.
Questions
- What is BIP 323?
- A proposal by Matt Corallo to reserve 24 bits of the block header's version field (bits 5 to 28) as extra nonce space for miners. It replaces BIP 320, which reserved 16.
- Why do miners need more nonce space?
- Header-only mining keeps ASICs away from transactions and Merkle trees, but each ASIC needs a steady supply of fresh work. More bits to roll in the header means less work from the controller. Some devices had started rolling 7 bits of the timestamp instead.
- Does BIP 323 need a soft fork?
- No consensus rules change. Nodes are asked to ignore bits 5 to 28 for soft-fork signalling and unknown-fork warnings; non-upgraded nodes may show warnings.
- What does it mean for future soft forks?
- Future soft forks should not use bits 5 to 28 for activation signalling. The BIP notes that no soft fork currently signalling uses them.
Sources
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