Definition
A stale share is a proof of work that your miner computed correctly but submitted too late: by the time the pool received it, a new block had already been found and the pool had moved on to a fresh template. The work was real, but it no longer applies to the job the pool is now tracking, so it is discarded. Stale shares are fundamentally a latency problem, not a hardware fault.
Why stale shares happen
Most stale shares cluster in the few milliseconds immediately after a block is found anywhere on the network. During that window your miner is still hashing against the previous job until it receives the new one. Network round-trip time, pool server distance, and slow job propagation all widen this window. On pools that adjust your work target on the fly, stale shares can also spike briefly during a difficulty transition. A small stale percentage is normal and unavoidable at every scale.
Keeping the rate low
You reduce stale shares by mining on a geographically close pool endpoint, using a stable low-latency connection, and running firmware that handles new-job notifications promptly. Protocol design matters too: newer transport that pushes job updates faster shrinks the stale window. A persistently high stale count usually points to a flaky link or an overloaded control board rather than the ASICs themselves.
Stale shares are counted within your overall reject rate, and they behave differently from a network orphan block, which is a fully mined block that loses a race at the same height.
In Simple Terms
A stale share is a proof of work that your miner computed correctly but submitted too late: by the time the pool received it, a…