What was the 2018 Monero hard fork to stop ASICs?
The 2018 Monero hard fork usually refers to the April 6, 2018 network upgrade, which changed Monero’s mining rules to stop existing specialized mining machines called ASICs from working on the upgraded network. The goal was to keep mining more accessible to people using ordinary computer processors and graphics cards, rather than letting purpose-built machines take over.
What changed in April 2018?
The upgrade activated at block 1,546,000. A block is a batch of transactions added to Monero’s shared transaction history, called the blockchain.
This was a hard fork: a rule change that required compatible, updated software. Older software could no longer follow the upgraded network’s rules.
For mining, Monero moved from its original CryptoNight algorithm to a modified version commonly called CryptoNight variant 1, or CryptoNightV7. A mining algorithm is the set of calculations your mining software performs to compete for block rewards.
The change was deliberately designed to make ASICs built for the previous CryptoNight rules incompatible. It did not make specialized mining hardware impossible forever. It made the existing designs unsuitable for mining the upgraded Monero chain.
Why were ASICs the concern?
An ASIC, short for application-specific integrated circuit, is a chip built for a narrow task. A mining ASIC can perform its intended calculations much more efficiently than general-purpose hardware.
In early 2018, manufacturers announced CryptoNight ASIC miners, including Bitmain’s Antminer X3. These machines challenged the idea that CryptoNight would keep Monero mining accessible on ordinary hardware.
The concern was not simply that someone had a faster machine. Monero’s developers and supporters worried about mining power becoming concentrated among:
- Manufacturers with control over specialized hardware.
- Buyers who could afford large numbers of those machines.
- Operators with early or privileged access to new equipment.
If you mined with a CPU, your computer’s main processor, or a GPU, its graphics processor, that concentration could make it much harder for you to compete.
Did the fork actually stop ASICs?
It stopped ASICs designed for the old CryptoNight rules from mining valid blocks on the upgraded network. After the fork, Monero’s reported network hashrate—the estimated total mining calculation rate—fell sharply.
That drop was consistent with substantial mining power leaving the network. However, you should not treat it as an exact count of ASICs: miners who failed to update also stopped contributing valid work.
Some groups continued chains using the old rules. Those were separate networks, not the upgraded Monero network.
The protection was also temporary by design. Hardware makers could develop new machines for revised algorithms. Monero made another CryptoNight change in October 2018, continuing its efforts to resist specialized miners.
How does this relate to mining today?
The April 2018 fork did not introduce RandomX. Monero adopted RandomX on November 30, 2019, replacing the CryptoNight variants with a different mining algorithm designed to favor CPUs.
That distinction matters if you find old guides or hardware listings. A machine advertised as a “CryptoNight Monero miner” does not thereby support Monero today. If you explore browser mining, you should also check what work the service actually performs and how it pays you.
The bottom line
The April 2018 hard fork was a targeted response to CryptoNight ASICs. It disabled those existing machines on Monero’s upgraded chain, but it was one step in an ongoing effort—not a permanent guarantee against specialized hardware.
