Share (Mining)
A share is a proof-of-work submission from a miner to a mining pool, demonstrating active computational effort at a lower difficulty target.
Definition
A share is a proof-of-work submission from a miner to a mining pool that meets a difficulty target lower than the full Bitcoin network difficulty. Shares prove that a miner is actively contributing computational effort even when no one in the pool has yet found a real block. They are the unit of measurement that pools use to allocate rewards fairly across thousands of participants whose individual hash rates may differ by many orders of magnitude.
How It Works
When a miner connects to a pool over the Stratum protocol, the pool issues mining jobs together with a target far easier than the live network difficulty. Each time the miner finds a hash that beats this pool target, it submits the result as a share. The pool validates the share against the job it issued, credits the miner’s account, and discards the submission once recorded.
The pool tracks the running volume of shares submitted by each participant. When the pool eventually finds a hash that also satisfies the actual network difficulty target, that block is broadcast to the network and the block reward is distributed proportionally to recent share contributions, minus the pool’s fee. A share that happens to also satisfy the network target is itself a valid block — but the vast majority of shares only ever serve as accounting records and never reach the broader network.
Why It Matters
Shares are the foundation of fair payout in pooled mining. Without them, a pool would have no transparent way to measure individual contributions, since one miner with a tiny fraction of the pool’s total hash rate may go years between blocks if measured solely by block discovery. Shares smooth that variance into something close to a steady income stream.
The pool’s chosen share difficulty is also a tradeoff. A low target produces many small shares, more bandwidth, and finer-grained accounting; a high target produces fewer submissions, less network overhead, but coarser variance for small miners. Most pools tune share difficulty per connection based on the miner’s reported hash rate.
Related Terms
Shares are best understood alongside the surrounding mining-pool concepts that determine how they are issued, counted, and paid out:
- What Is a Mining Pool — where shares are submitted
- Hash Rate — what determines share volume
- Mining Difficulty — the network target shares aspire to
- Stratum Protocol — the protocol carrying shares