Can selfish mining be done on Monero?

Yes—in principle, selfish mining can be attempted on Monero. It means deliberately hiding valid blocks and releasing them at carefully chosen moments to try to earn a larger share of mining rewards. But being able to attempt it does not mean it will be profitable, especially for a small miner.

What selfish mining would look like

Normally, when a Monero miner finds a valid block—a batch of transactions added to the blockchain—they broadcast it so other miners can build on it.

A selfish miner instead keeps that block private and mines a hidden continuation of the chain. They later release some or all of those blocks to compete with the public chain.

Monero nodes, the computers that check and share blockchain data, choose between valid competing chains using cumulative proof of work. That means the total mining work represented by a chain, rather than simply its number of blocks.

If the hidden chain wins, some honest miners’ blocks become stale: valid blocks that are not part of the accepted chain and earn no block reward. The selfish miner hopes to make competitors waste more work than they do.

Why Monero is not automatically immune

Monero’s privacy features hide transaction details. They do not prevent miners from withholding blocks.

Its mining algorithm, RandomX, has been used since November 30, 2019. It favors CPUs—the general-purpose processors in ordinary computers. That changes which hardware can compete effectively, but it does not remove the incentive problem behind selfish mining.

Other Monero features matter, without providing a complete defense:

• Blocks arrive about every two minutes. How quickly blocks spread affects who wins close races.
• Difficulty adjusts every block. Difficulty controls how hard finding a block is. Any profitability analysis needs to account for Monero’s adjustment rules.
• Tail emission pays 0.6 XMR per block, plus transaction fees. This ongoing reward gives miners something to compete for, including through dishonest coordination.

These features mean you should not assume an analysis of another cryptocurrency applies unchanged to Monero.

There is no universal profitable threshold

You may see claims that selfish mining becomes profitable at “25%” or “one-third” of mining power. Those figures come from particular mathematical models, not a guaranteed Monero threshold.

The result depends on factors such as:

• Your share of total mining power, also called hashrate.
• How quickly your blocks reach other miners.
• Which branch other miners choose during a tie.
• The withholding strategy and difficulty-adjustment behavior.

A small miner can hide blocks, but will usually struggle to build a private lead. If their hidden branch loses, they sacrifice rewards they might have earned by publishing promptly. Selfish mining can theoretically benefit an attacker below majority control, but it is not a reliable shortcut to higher earnings.

What this means for browser mining

If you mine through a browser connected to a pool—a service that combines miners’ work—you generally do not control block publication or which chain the pool builds on. That control usually sits with the pool’s operator or mining infrastructure.

Promises of “selfish mining profits” for ordinary browser users deserve skepticism. Ask where rewards actually come from, and never treat a claimed percentage boost as guaranteed.

The bottom line

Monero can face selfish-mining attempts, but profitable execution depends on mining power, network conditions, and strategy. For you as a browser miner, it is mainly a network-security concern—not a practical earnings feature.