Orphan Block
An orphan block is a block that was found honestly but never made the chain: the network accepted a competing one at the same moment. The work behind it burns.
Where orphans come from
Two miners sometimes find a block almost simultaneously. Both versions spread across the network, some nodes see the first, some the second. The fork lives until the next block: whichever branch got extended is the real one, and the rival becomes an orphan.
The orphan's reward disappears with it. For a solo miner that is a whole block lost, for a pool the loss is spread by the payout scheme: on PPLNS everyone in the window shares it, on PPS the pool takes it on itself.
It happens rarely. Blocks fly across the network in seconds these days, and the orphan share in big networks stays at a fraction of a percent. For income it is background loss, not a visible one.
The miner has one lever: latency. The slower your pool learned about a new block and the slower your shares reach the pool, the higher the chance of working on a branch that has already lost. It is the same mechanism as stale shares, just with higher stakes.
The short version
| What happened | two blocks found almost at once |
| Who decides | the network: the extended branch wins |
| The reward | burns with the orphan |
| How often | a fraction of a percent of blocks |
| The miner's lever | lower latency to the pool |
What depends on you here
Pick a pool with servers close to you: less ping, less work on dead branches.
Watch stale shares: their growth and orphan risk grow from one root, latency.
Keep orphans in mind when reading news: 'pool lost a block' sounds scary, in money terms it is ordinary background network statistics.
Going solo, account for it: a rare found block can still fail to stick, and that is part of the price of solo mining.
An example from network life
A pool found a block and credited members the reward with an unconfirmed status. A minute later the network extended the competing branch, the block became an orphan, and the credit vanished from the stats. For members on PPS nothing changed: the pool prices this kind of variance into its fee.
Related terms
Where to go next on the site
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- ASIC Miner knowledge base
Questions and answers
Is an orphan an attack on the network
No, it is normal operation of a distributed system: simultaneous finds are inevitable. Attacks are built on something else, on a majority of hashrate.
Why did a block payout vanish from the pool stats
Most likely the block became an orphan before confirmations. That is exactly why pools show the reward as immature until the network locks the block in.
Can an ASIC avoid working on orphans entirely
No, while the work is running nobody knows which branch will win. You can only cut latency, you cannot remove the risk completely.
How the terms connect
Every link in the chain is clickable. Orange marks where you are now.
Looking for an ASIC miner
The catalog holds 212 models. You can compare them by hashrate and by joules per terahash, then plug your own rate into the calculator and see what stays in your pocket.
Page written and checked by Denys Klimchuk. Updated .