PPLNS (Pay Per Last N Shares)

What Is PPLNS?

PPLNS (Pay Per Last N Shares) is a reward distribution method used by mining pools to allocate block rewards and transaction fees among participating miners. Instead of paying miners for every share they submit regardless of whether the pool finds a block, PPLNS only distributes rewards after the pool successfully mines a block, and it calculates each miner's share based on the last N shares submitted before that block was found.

The method was introduced to solve a specific problem with earlier proportional payout schemes: pool hopping. In a simple proportional system, miners could maximize earnings by mining at a pool only during the early phase of a round and then switching to another pool. PPLNS eliminates this exploit by using a fixed-size sliding window rather than round boundaries to determine payouts.

PPLNS remains one of the most common payout methods alongside PPS, FPPS, and PPS+. The choice between them reflects a fundamental tradeoff: who bears the variance of block discovery, the pool operator or the miners.

How It Works

To understand PPLNS, it helps to first understand how mining pools distribute work. Miners submit shares: partial solutions that prove they are actively hashing. Shares do not solve a block on their own, but they demonstrate that the miner is contributing hashrate to the pool. When one of those hashes happens to meet the network's difficulty target, the pool finds a block and earns the block subsidy plus transaction fees.

Under PPLNS, the pool maintains a sliding window of the most recent N shares submitted across all miners. When a block is found, the pool looks at this window and distributes the reward proportionally based on how many of each miner's shares fall within it.

1. Miners submit shares continuously as they hash against the pool's work template
2. The pool records each share in a rolling buffer of size N
3. When the pool finds a valid block, it examines the last N shares
4. Each miner's payout is calculated as: (miner's shares in window / N) multiplied by the total block reward
5. Older shares that have fallen outside the window receive nothing for that block

Choosing the Window Size N

The value of N is a critical parameter that pool operators must set carefully. It is often expressed as a multiple of the pool's expected shares per block (related to the share difficulty and the network difficulty).

• A small N (close to 1x the expected shares per block) increases variance because miners who contributed shares early in a long round may see their work fall outside the window
• A large N (2x to 4x the expected shares per block) smooths payouts and ensures most contributed work is rewarded, but reduces the anti-hopping benefit because hoppers can linger longer
• Many pools set N to approximately 2x the expected shares per round, which balances fairness with hopping resistance

Academic research on PPLNS, including the analysis by Meni Rosenfeld, suggests that the window should be large enough that the vast majority of blocks are found within the window period. Some pool operators dynamically adjust N after each block to maintain this balance.

Simplified Payout Calculation

// Simplified PPLNS payout calculation
const windowSize = 1_000_000; // N: last 1 million shares
const blockReward = 3.125;    // BTC (current subsidy)
const txFees = 0.15;          // BTC from transaction fees
const totalReward = blockReward + txFees; // 3.275 BTC

// Miner submitted 50,000 shares in the window
const minerShares = 50_000;
const minerPayout = (minerShares / windowSize) * totalReward;
// minerPayout = 0.16375 BTC (5% of total reward)

PPLNS vs Other Payout Methods

The major payout methods differ in who bears the risk of block-finding variance and transaction fee fluctuations. For a detailed comparison, see the mining pool payout method comparison.

Under PPS, the pool pays a fixed rate per valid share regardless of whether the pool finds a block. The pool absorbs all variance, which is why PPS fees are higher. FPPS extends PPS by also including an estimated share of transaction fees. PPLNS, by contrast, passes both block-finding variance and fee fluctuations through to miners, but compensates with lower fees.

Why PPLNS Discourages Pool Hopping

Pool hopping is a strategy where miners switch between pools to exploit round-based payout schemes. In a simple proportional system, shares submitted early in a round are disproportionately valuable because fewer total shares exist when a quick block is found. Hoppers mine early, leave if the round runs long, and rejoin fresh pools.

PPLNS defeats this strategy because:

• The window is not tied to round boundaries: it always covers the last N shares regardless of when blocks are found
• A miner who leaves and returns loses the shares that aged out of the window during their absence
• A newly arrived miner has few shares in the window and receives a proportionally small payout if a block is found immediately
• Consistent miners accumulate a steady presence in the window and receive reliable payouts over time

This makes PPLNS inherently fairer for loyal miners who contribute consistently rather than strategically timing their participation.

Use Cases

Long-Term Mining Operations

PPLNS is well-suited for miners who run hardware continuously, such as mining farms with dedicated ASIC miners. These operations benefit from the lower fees because their consistent uptime means they always have shares in the window. Over long periods, the variance smooths out and the fee savings compound.

Pools Prioritizing Fairness

Pool operators who want to attract committed miners often choose PPLNS because it naturally filters out opportunistic hoppers. The method rewards loyalty without requiring explicit lockup periods or penalties. Some pools combine PPLNS with variable difficulty adjustments to further optimize share submission rates for miners of different sizes.

Transaction Fee Capture

Unlike pure PPS, PPLNS distributes both the block subsidy and transaction fees to miners. As the block subsidy decreases through halvings, transaction fees become an increasingly important component of mining revenue. PPLNS miners capture the actual fees included in found blocks, which can exceed estimated fee payouts used by FPPS during periods of high network congestion.

Risks and Considerations

Higher Short-Term Variance

The most significant tradeoff with PPLNS is income volatility. If the pool goes through an unlucky streak and finds fewer blocks than expected, all miners earn less during that period. Conversely, a lucky streak pays above average. This variance can be challenging for miners with thin margins or those who need predictable cash flow to cover electricity costs.

For context on how mining economics affect profitability decisions, see the Bitcoin mining economics analysis.

Delayed Ramp-Up for New Miners

When a miner first joins a PPLNS pool, their share of the window is initially small. It takes time to fill the window with their shares, meaning early payouts are proportionally lower. This cold-start period can make PPLNS feel unrewarding compared to PPS, where miners earn from the first share submitted.

Pool Size Matters

Smaller pools find blocks less frequently, which amplifies the variance inherent in PPLNS. A pool that finds one block per day exposes miners to significant day-to-day income swings. Larger pools that find multiple blocks per hour effectively smooth out the variance, making PPLNS behave more like a steady payout. This dynamic contributes to mining centralization, as miners gravitate toward larger pools for more predictable returns.

Block Withholding Attacks

PPLNS pools remain vulnerable to block withholding attacks, where a malicious miner submits valid shares but discards any share that would actually solve a block. The attacker still collects their share of rewards from blocks found by honest miners while preventing the pool from earning revenue on the withheld blocks.

Verification Difficulty

Miners must trust that the pool operator correctly implements the PPLNS window and distributes rewards fairly. Unlike PPS (where payouts can be verified against expected values per share), PPLNS payouts depend on the total shares in the window and the timing of block discovery, making independent verification harder. Modern protocols like Stratum V2 aim to improve transparency by giving miners more visibility into pool operations.

Why It Matters

The choice of payout method shapes the economics of proof-of-work mining and influences how hashrate distributes across pools. PPLNS represents one end of the risk spectrum: miners accept variance in exchange for lower fees and direct exposure to actual block rewards. As the block subsidy continues to halve and transaction fees grow as a proportion of total mining revenue, the ability to capture real fee revenue (rather than pool-estimated averages) may make PPLNS increasingly attractive for miners with the capital reserves to weather short-term variance.

For Bitcoin's broader ecosystem, payout methods also affect network health. Mechanisms that discourage pool hopping and reward consistent participation help maintain stable hashrate distribution, which strengthens the network's censorship resistance and security.

This glossary entry is for informational purposes only and does not constitute financial or investment advice. Always do your own research before using any protocol or technology.