Shares on a Pool
“Shares” are how the pool tracks how much mining work you actually do.
The pool gives you a Difficulty level, and your miner reports a solution every time it finds one that meets the threshold. This Difficulty the pool sends you is much easier than the actual Difficulty of finding THE SOLUTION to the current block… if you find THE SOLUTION, it will be reported, but so will a lot of easier-to-find solutions that don’t qualify as THE SOLUTION.
Since the pool knows what Difficulty level they gave you, they can tell how much work you’re actually doing by seeing how many valid shares you submit.
Made-up numbers for an example:
Say the real Difficulty on chain is such that finding the solution is one in 1,000,000,000. And you won’t find one for a long time, because you only produce about 100 tries per second… takes you 115 days! That’s why you join a pool.
You mine: 100 per second
Pool-assigned Difficulty: you can find 1 in 1000
You report shares: about 1 every 10 seconds
Computed rate: 1000/10 = 100
The pool knows that if you’re sending in shares at roughly every ten seconds, and Difficulty is 1 in 1000, you must be mining at 100 per second. That’s how much work you’re really contributing.
Same work contribution you expect, same profit share, on average. The pool must spend processing power verifying every share you submit, so they try not to pick a setting where all their miners are constantly submitting shares. If everyone submitted 100 attempts per second, the pool would be overwhelmed and unable to process all the data.
Your miner reports what your real hashrate is to you, and may also send it to the pool - why doesn’t the pool accept that?
Because you could write a miner that just reports a higher hashrate than you really have. You can potentially lie!
But when you send in shares, then you’re sending in proof that you’re really working.
The shares are quite literally “proof of work.”
This is why the mining algorithm is called a “PoW” or “Proof of Work” algorithm. The fact that you find the result is proof that you must have been doing the work.
(Some pools do show your “reported” hashrate, and will chart it versus your actual hashrate from submitted shares, but they will only pay you on shares…)