What is RandomX?

RandomX is the set of computing rules Monero uses to mine new blocks and help keep its network secure. It is designed to work well on ordinary computer processors, called CPUs, rather than give specialized mining machines a big advantage. Monero switched to RandomX on November 30, 2019, replacing its earlier CryptoNight-based mining algorithms.

What RandomX actually does

When you mine Monero, your computer performs calculations to find a result that meets the network’s current target. This is called proof of work: your computer must do real computing work, but other computers can check its answer quickly.

RandomX defines those calculations. Rather than repeating one simple operation, it runs a changing mix of small programs and memory operations. The work is designed to resemble tasks that general-purpose CPUs already handle well.

Despite the name, the results are not unpredictable once the inputs are known. Given the same inputs, every computer can verify the same result. That consistency lets the network agree that a miner’s work is valid.

Finding a valid result lets a miner propose a new block—a batch of transactions added to Monero’s shared record.

Why Monero uses it

Some mining systems favor ASICs, which are machines built to perform one narrow task extremely efficiently. They can leave ordinary computers unable to compete.

RandomX tries to reduce that advantage by requiring a broad mix of processor features and substantial memory. Building a specialized chip that beats a good CPU becomes harder and less attractive.

For you, that means:

• A normal desktop CPU can be useful for Monero mining.
• A graphics card, or GPU, is generally less competitive for RandomX.
• You do not need a purpose-built mining machine to participate.

This does not mean every CPU earns a profit, or that specialized hardware is impossible. RandomX is ASIC-resistant, not a guarantee that no specialized design could ever gain an advantage.

Why memory matters

RandomX needs more than raw processor speed. It also relies on fast access to memory.

Its two operating modes have different requirements:

• Fast mode uses a dataset of about 2,080 MB in memory. This is the usual choice for efficient mining.
• Light mode uses a 256 MB cache, a smaller store of working data, but performs the calculations much more slowly.

For efficient mining, you generally want about 2 MB of L3 cache per mining thread. L3 cache is fast memory inside your processor. A thread is one stream of work your processor handles.

That is why using every available CPU thread does not always improve performance. Threads can compete for limited cache and memory access.

What it means for browser mining

RandomX favoring CPUs does not mean a browser performs like dedicated mining software. Browser limits, memory handling, and fewer hardware optimizations can make direct RandomX mining much slower or impractical on some devices.

A website showing an XMR balance also does not prove it is running RandomX. It might mine something else and pay you in Monero. Check what work your device actually performs, along with fees and withdrawal rules.

Mining also uses electricity and produces heat. Only run it on devices you own or have clear permission to use.

The bottom line

RandomX makes general-purpose CPUs a practical part of Monero’s security. Its changing calculations and memory demands discourage specialized mining hardware, but they do not promise easy earnings—or efficient mining in your browser.