A mining pool's orphan rate shows how often its found blocks fail to remain on Bitcoin's active chain. But the effect on a miner's BTC earnings depends on more than that percentage: the measurement period, sample size, and payout method all matter.
This article explains orphan rate and how ViaBTC's PPS+ and PPLNS methods distribute the associated risk. It does not report a current ViaBTC orphan-rate figure; the formula and examples below explain the general metric rather than a verified ViaBTC dashboard methodology.
What Is a Mining Pool's Orphan Rate?
In Bitcoin, two miners or pools can find valid blocks at the same height at nearly the same time. If the active chain ultimately builds on one competing branch, a block on the losing branch becomes a stale block. Its coinbase transaction, which claims the block subsidy and transaction fees, is not part of the active chain.
“Orphan block” is often used informally to mean a stale block. Strictly, however, it can also mean a block whose parent is not yet known to the receiving node. These are different concepts, as the Bitcoin Developer Guide explains.
For this article, orphan rate means the proportion of a pool's valid found blocks that became stale:
Orphan rate (%) = stale blocks ÷ (main-chain blocks + stale blocks) × 100%
Both counts must refer to blocks found by the same pool, on the same coin, within the same measurement period, using consistent attribution and classification rules.
For illustration only—not as an actual ViaBTC figure—a pool that found 1,000 valid blocks, including two that became stale, would have an orphan rate of 0.2%.
A pool's share of network blocks, a network-wide fork statistic, and a miner's rejected-share percentage measure different things. None should be substituted for a pool-specific orphan rate.
Why Do Stale Blocks Happen?
Block propagation is not instantaneous. When competing valid blocks are broadcast at nearly the same time, different nodes may receive different blocks first. Miners can temporarily work on separate chain tips. As one branch accumulates more proof of work, nodes follow that branch, leaving blocks on the other branch stale.
A pool's exposure depends partly on how quickly it validates and broadcasts a newly found block, receives competing blocks, and updates mining jobs. Node connectivity, bandwidth constraints, and network latency can also affect propagation. Bitcoin Core's compact block relay documentation explains how relay methods reduce bandwidth use and can shorten propagation delays.
Here, network congestion means constraints affecting communication between nodes. A backlog of unconfirmed transactions or higher transaction fees does not, by itself, establish that stale-block risk has increased.
Occasional competing blocks are an expected feature of Bitcoin mining. A single stale block is not, on its own, evidence of an operational fault.
The Revenue Impact of a Stale Block
A stale block does not earn an on-chain reward for the pool that found it. Its coinbase transaction is outside the active chain, so the pool cannot collect that block's subsidy or transaction fees through it.
Bitcoin's block subsidy has been 3.125 BTC since the halving at block 840,000 on April 20, 2024. Transaction fees are additional and vary by block. See Bitcoin.org's halving history.
The effect on an individual miner's account is a separate question. Some payout methods pay for accepted work independently of individual block outcomes; others distribute rewards from blocks the pool actually finds and confirms.
How Payout Method Changes the Impact: PPS+ vs. PPLNS
ViaBTC offers PPS+ and PPLNS for Bitcoin mining. Its official calculation rules distinguish the subsidy portion of earnings from transaction-fee earnings. Below, subsidy component refers to the portion labeled “Block Reward” in ViaBTC's documentation.
PPS+: Different Rules for the Two Components
Under PPS+, the subsidy component follows PPS rules. It is calculated from valid shares and current network difficulty, settled hourly, and subject to a 4% pool fee.
Because this credit is based on accepted work rather than the fate of a particular pool-found block, a stale block does not directly remove a corresponding subsidy credit from the miner's account. This means the pool bears the immediate stale-block risk for that component.
The transaction-fee component follows PPLNS rules and carries a 2% fee. It is calculated using users' hashrate contributions over the last five difficulty rounds when a block completes six confirmations. It therefore depends on actual confirmed block results and remains exposed to stale-block outcomes.
PPS+ consequently has two calculation methods and two component-specific fee rates, rather than one flat fee applied to all earnings.
PPLNS: Both Components Depend on Block Results
Under PPLNS, the subsidy and transaction fees are calculated together, with a 2% pool fee. Allocation uses users' hashrate contributions over the last five difficulty rounds when a block completes six confirmations.
A block that becomes stale before meeting that settlement condition does not produce a reward for distribution under those rules. PPLNS miners are therefore directly exposed to the pool's realized block results, including variation from pool luck and stale blocks.
The distinction is straightforward: PPS+ separates the subsidy component from individual block outcomes, while PPLNS ties both components to the pool's confirmed blocks. PPS+ transaction-fee earnings also remain tied to those results.
Orphan Blocks, Stale Shares, and Rejected Shares
These terms describe different events:
- An orphan or stale block is a block-level outcome: a valid block does not remain on the active chain.
- A stale share is a submission based on an outdated mining job that the pool no longer accepts. For example, after a chain-tip update, a delayed miner may continue working on the previous job. Issuing a newer job does not necessarily invalidate every earlier job.
- A rejected share is a submission the pool does not accept. Common reasons include stale work, duplicate submissions, and invalid results. Pools and miner interfaces may report these categories separately, so check the platform's definitions before comparing percentages.
ViaBTC similarly describes stale shares as work that is no longer current when it reaches the pool in its guide to miner uptime.
A high rejected-share percentage does not establish that the pool has a high orphan rate. Miner-to-pool submission problems and pool-level block outcomes need to be assessed separately.
Interpreting Orphan Rate Statistics Responsibly
Sample size matters. In a hypothetical sample of 100 valid found blocks, one stale block produces a 1% orphan rate. In a sample of 1,000, one stale block produces a 0.1% rate. A small sample can therefore show a large percentage change after a single event.
For comparisons between pools, use the same coin and observation window, consistent block attribution, and matching definitions of the numerator and denominator. For comparisons over time, use clearly specified, comparable windows. In either case, consider whether enough blocks have been observed to support the conclusion.
A short period dominated by chance should not become a lasting performance ranking. The rate alone also does not identify the cause of stale blocks or translate directly into an equal percentage loss in an individual miner's earnings.
This analysis is specific to Bitcoin. Other proof-of-work networks may treat competing blocks and rewards differently.
Conclusion
Orphan rate can help assess block-propagation performance, but it needs context. All else equal, fewer stale blocks mean more pool-found rewards remain available. The effect on miners depends on the payout method: ViaBTC PPS+ shields the subsidy component from individual stale-block outcomes, while its transaction-fee component and PPLNS earnings depend on confirmed block results.
BTC mining revenue also depends on accepted work, network difficulty, transaction fees, pool fees, and the payout method's exposure to pool luck. Electricity and hosting costs then affect net profitability. Keeping those measures separate makes orphan-rate comparisons more useful.
FAQ
Is a stale block the same as an orphan block?
In informal mining usage, the terms often describe the same event: a valid block that did not remain on the active chain. Strictly, an orphan block can also mean a block whose parent is unknown to a node, which is a different condition.
Does a lower orphan rate guarantee higher mining revenue?
No. It means a smaller proportion of found blocks became stale under the stated measurement method. BTC earnings also depend on accepted work, difficulty, fees, payout rules, and exposure to pool luck. Electricity and hosting costs affect net profitability rather than directly determining the BTC revenue credited by the pool.
Does orphan rate affect PPS+ and PPLNS miners the same way?
No. ViaBTC's PPS+ subsidy component is calculated from shares and difficulty, so an individual stale block does not directly reduce that credit. Its transaction-fee component follows PPLNS rules. Under PPLNS, both components depend on the pool's confirmed block results.
Are stale shares the same as orphan blocks?
No. A stale share relates to work submitted for a job the pool no longer accepts. An orphan or stale block relates to a valid block that does not remain on the active chain. They are different metrics, even though network delays can contribute to both.