Miner signaling is how Bitcoin miners indicate readiness to enforce a proposed soft fork. Miners set specific bits in the nVersion field of blocks they mine. Once enough blocks in a difficulty adjustment period signal support, the soft fork can lock in and eventually activate.
Bitcoin's mining difficulty adjusts every 2,016 blocks — approximately every two weeks at the target rate of one block per 10 minutes. BIP9 uses this same window to tally miner signaling. If enough blocks within one period signal support, the soft fork locks in.
BIP9 is the standard mechanism for coordinating soft fork activations. Each proposal is assigned a version bit (0–28). Miners set that bit in their block's version field to signal readiness. If the required percentage of blocks in a single 2,016-block period signal support, the soft fork locks in. After one further grace period (~2 weeks), the new rules become active and non-compliant blocks are rejected by upgraded nodes.
BIP-110 (Reduced Data) is a proposed temporary soft fork that limits the size of data fields in Bitcoin transactions to reduce blockchain bloat and refocus development on monetary use cases. It uses version bit 4 and requires 55% of blocks in a difficulty period to signal support. Track it live at bip110monitor.com.
BIP-119 (OP_CHECKTEMPLATEVERIFY) proposes a new opcode that allows a script to commit to how its funds may be spent, enabling covenants, vaults, and more efficient payment channels. It uses version bit 5 and requires 90% of blocks to signal support. Track it live at bip119monitor.com.
Signal rates are fetched in real time from the public APIs of each individual monitor. Each monitor tracks miner signaling using block data from mempool.space, checking the nVersion field of every block since tracking began. Data updates on every new Bitcoin block via a webhook.
Each proposal sets its own activation threshold based on the level of miner consensus deemed sufficient for safe activation. BIP-110 uses 55% while BIP-119 uses 90%. A higher threshold reduces the risk of a contentious activation but makes it harder to reach lock-in.