Bitcoin’s security risk starts when one block gets far more fees than the next
Bitcoin’s security-budget debate normally starts with one complete: how a lot miners gather in transaction fees as the block subsidy shrinks.
A July 2026 NBER working paper by Fabian Schär, Dario Thürkauf, and David Yermack factors to a second variable. Using information from 2017 via 2025, the authors report that bigger charge variations between adjoining Bitcoin blocks are related to more competing blocks at the identical top and an extended anticipate the next block.
The proof is observational and identifies a network-level relationship, whereas miner intent and the reason behind any particular person block race stay unresolved. The discovering nonetheless provides wallets, miners, and customers a measurable sign: Bitcoin security incentives reply to how fees arrive from block to block, in addition to how a lot the community pays over time.
Fee gaps create a special mining incentive
Bitcoin at the moment pays miners a set subsidy of three.125 BTC for every block, plus the transaction fees included in that block. Successive subsidy reductions place more long-run weight on fees as a supply of mining income.
As of Aug. 26, a every day Glassnode measure put transaction fees at about 0.70% of miner revenue. A BTC.network report covering Aug. 14 through Aug. 21 calculated a 0.67% share for the week. The two snapshots cowl totally different intervals, however every locations fees beneath 1%.
Block-level information can present a lot sharper variation than these mixture readings. An Aug. 26 Blockchain.com block snapshot confirmed 0.0077 BTC in fees in block 964,120 and 0.0536 BTC in block 964,121, an nearly seven-fold change between adjoining blocks. The comparability illustrates how sharply charge rewards can range from one block to the next, whereas the charge values alone go away miner conduct unresolved.
That prize shapes the alternative described by Bitcoin Optech’s fee-sniping reference. A miner can prolong the latest block and compete for the transactions at the moment ready in the mempool. It also can try to recreate a helpful prior block, declare that block’s fees, after which prolong the various chain.
The try begins behind the accepted tip, and its financial attraction rises when fees in the prior block tremendously exceed the anticipated fees in a brand new tip-extending block. Hash-rate share, propagation, and different miners’ reactions have an effect on the odds, so the incentive is probabilistic. Variable fees can change the payoff calculation even in periods when the community’s mixture charge income is low.
The working paper exams whether or not that logic seems in historic community conduct. In a co-author explanation of the research, Thürkauf defines a block race as competing blocks at the identical top. The authors affiliate bigger adjacent-block charge gaps with more of these races.
They additionally report a decrease chance that the next block seems in the first seconds after a big charge hole, a timing sample in keeping with some hash fee contesting the prior top. Since the evaluation is observational, the end result establishes an affiliation at the community stage and leaves particular person miner motives unresolved.
That distinction shifts the measurement focus as a result of month-to-month or annual charge totals describe Bitcoin’s total security earnings, whereas adjacent-block charge gaps isolate temporary intervals when revisiting the prior top can carry a bigger potential payoff.
| Signal | Security relevance | Interpretive restrict |
|---|---|---|
| Fee hole between adjoining blocks | Approximates the further prize in a helpful prior block | Miner intent stays unknown |
| Competing blocks at the identical top | Shows that a number of variations briefly existed | Routine community conduct also can produce a race |
| Delay in the next block’s first seconds | Matches the timing window highlighted by the research | A single delay has a number of doable causes |
| Fee share of miner income | Measures mixture reliance on transaction fees | Fee distribution stays exterior the mixture measure |
Bitcoin pockets protections shrink the prize erratically
Bitcoin transactions can cut back the incentive to revisit a previous block via lock fields. A pockets can set a lock so the transaction first turns into mineable in the block after the present tip, which excludes it from a substitute of the present tip.
Widespread use modifications the economics of charge sniping as a result of a miner rebuilding the earlier top loses entry to a few of the latest pending transactions, decreasing the income accessible in its various block. The safety shrinks the accessible prize and leaves reorganization makes an attempt technically doable.
Bitcoin Optech’s technical overview says builders see present protections as incomplete. Their effectiveness is dependent upon which wallets and transaction-creation methods set the related fields, how constantly they accomplish that, and which transaction varieties they cowl.
BIP 326 describes anti-fee-sniping conduct for Taproot transactions via nLockTime or nSequence. It stays a draft informational proposal, and wallets can undertake the strategy step by step beneath current consensus guidelines, leaving real-world protection depending on implementation decisions.
An open Bitcoin Core issue from April 2026 paperwork one concrete inconsistency. The difficulty says the ship RPC and GUI pockets movement set nLockTime close to the present block top, whereas the createrawtransaction and walletcreatefundedpsbt paths default to zero. The proposed consistency change stays open.
The distinction means Bitcoin Core’s anti-fee-sniping default is utilized erratically throughout transaction-creation paths. Estimating the network-wide impact would require information on how a lot transaction quantity every path represents, which the difficulty doesn’t present.
Implementation protection subsequently belongs inside the security-budget dialogue as a result of a mitigation might be technically accessible whereas its community impact is dependent upon the share of pending transactions that use it. Broader and more constant lock-field conduct would scale back the fees accessible to a miner making an attempt to rebuild the earlier top.
Miners additionally face a coordination drawback as a result of the return from contesting a block relies upon partly on whether or not different miners prolong the accepted tip. A broad migration towards protecting transaction building modifications the accessible reward instantly and might happen beneath current consensus guidelines, avoiding a miner-coordination requirement.
Signals to observe earlier than the next subsidy reduce
The next subsidy discount offers a helpful monitoring horizon, although its security results will depend upon charge demand, charge distribution, miner conduct, propagation, and mitigation adoption.
Four indicators present a greater view than mixture income alone:
- Adjacent-block charge gaps. Persistent or excessive gaps mark the intervals when a previous block carries the largest further prize.
- Competing-block frequency. A change in same-height races exhibits shifting community conduct whereas leaving the trigger open.
- Immediate next-block timing. The first seconds after a high-fee block are the interval highlighted by the research.
- Lock-field protection. More constant use throughout pockets and automatic transaction-creation paths can cut back the income accessible in a rebuilt prior block.
Each sign captures a special a part of the incentive as a result of charge gaps describe the prize, block races and timing describe community outcomes, and lock-field use describes a protection.
Bitcoin’s charge market can produce occasional outlier blocks even whereas fees stay a small share of miner income. Those outliers deserve nearer consideration as a result of mining incentives emerge in every block interval, whereas month-to-month income charts blur the short-lived extremes.
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