Can websites mine Monero in my browser without my knowledge?

Yes. A website can run mining code in your browser without clearly telling you or asking you to agree. This hidden use of your device is called cryptojacking: someone uses your computing power to try to earn cryptocurrency while you bear the extra workload, heat, and electricity use.

How hidden browser mining happens

When you visit a page, your browser runs small programs that make the site work. A dishonest site can include a program that tries to mine cryptocurrency in the background. A legitimate site can also serve mining code accidentally if an attacker changes its files or compromises an outside service it uses.

You usually do not need to install an app for this to happen. Mining code can use ordinary browser features, so you may never see a permission prompt.

That is different from a site openly offering mining and letting you choose whether to start. Consent should be clear, not buried in a privacy policy or treated as automatic because you opened a page.

Is it really mining Monero?

It is possible, but there is an important catch: modern Monero mining is a poor fit for a typical browser.

Monero uses RandomX, its mining algorithm—the set of computing tasks miners perform to help secure the network. It favors your CPU, the main processor in your device, and its fast operating mode uses roughly 2 GB of memory just for its dataset. Browser restrictions and performance limits make useful mining harder than with dedicated mining software.

Many older reports about browser-based Monero mining describe technology used before Monero switched to RandomX in November 2019.

Today, a page claiming to “mine Monero” might actually:

• Try to mine Monero directly, with limited performance.
• Mine something else and pay rewards in XMR, Monero’s currency.
• Display fake mining activity without doing genuine mining.

A moving counter or a busy processor does not prove that a website is mining Monero.

Signs you can check

Hidden mining may cause:

• Fans to run loudly while an otherwise simple page is open.
• Unusual heat or faster battery drain.
• Sluggish browsing or sustained high CPU use.

These signs are clues, not proof. Video calls, games, and badly written pages can cause similar symptoms.

If your browser has a built-in task manager, use it to see which tab or extension is using the most CPU. Otherwise, check your device’s system activity tool. Close the suspicious tab and see whether the load drops.

Browser-only mining normally stops when the responsible page closes. If high usage continues, check other tabs, separate browser windows, and extensions. Continued activity does not automatically mean mining, but it deserves investigation.

How to protect yourself

Keep your browser and operating system updated. A reputable content blocker with mining-script protection can help, though no blocker catches everything.

Avoid sites that ask you to disable security tools, install an unknown extension, or turn off antivirus protection to “activate mining.” Never give a mining page your wallet’s recovery phrase, the secret words that control access to your funds.

If you suspect hidden mining, leave the site and run a scan with a trusted security tool if symptoms persist. You do not need to pay a “cleanup fee” demanded by a pop-up.

The bottom line

A website can attempt hidden mining without a browser permission prompt. Watch for unexplained device load, close suspicious pages, and remember that claims of “Monero mining” are not proof of what the code actually does.