Shares
Proof-of-work submissions from miners that demonstrate mining effort to the pool, used to calculate payout proportions.
What are Shares?
In pool mining, a share is a proof-of-work submission that demonstrates a miner is actively working on finding a block. Shares are hashes that meet a lower difficulty target than the actual Bitcoin network difficulty, making them much easier to find. The pool uses shares to fairly measure each miner's contribution.
How Shares Work
- The pool assigns each miner a share difficulty -- much lower than the network difficulty
- As miners hash, they find results that meet this lower threshold
- Each qualifying result is submitted to the pool as a "share"
- The pool counts shares to determine each miner's proportional contribution
- Occasionally, a share also meets the full network difficulty -- this is a valid block
Think of it like a lottery: the pool lowers the winning threshold so miners can prove they are buying tickets (hashing), even though the actual jackpot (a valid block) requires an even better result.
Share Difficulty
Pool share difficulty is adjustable and typically set so that miners submit shares at a manageable rate -- often every few seconds. Higher-hashrate miners usually receive higher share difficulty to reduce the volume of submissions while still accurately measuring their contribution.
The key insight is that share difficulty does not affect earnings. Whether you submit many low-difficulty shares or fewer high-difficulty shares, the expected contribution measurement is the same. The pool adjusts share difficulty for operational efficiency.
Stale and Rejected Shares
Not all submitted shares count toward payouts:
- Stale shares: Submitted after a new block was found, making them obsolete. Common with high-latency connections.
- Rejected shares: Invalid shares due to hardware errors or software bugs. A high reject rate indicates a problem.
A healthy mining setup should have a stale rate below 1-2% and a reject rate near zero. Monitoring these rates helps identify network latency issues or hardware problems before they significantly impact earnings.
Shares and Payout Methods
Every pool payout method uses shares as the fundamental unit of measurement, but they differ in how shares translate to payments. FPPS pays a fixed value per share, PPLNS counts shares in a window when blocks are found, and PPS+ uses shares for both guaranteed and variable components.