How to Stop Websites Using CPU Mining

Websites can secretly use your computer’s processing power to mine cryptocurrency, slowing down your device and increasing your electricity bill. This guide shows you how to block these scripts using browser settings, extensions, and network-level defenses, so you can browse safely and keep your CPU for yourself.

What You’ll Need

A modern web browser (Chrome, Firefox, Edge, Safari, or Brave)
Administrator access to install extensions (if using a work or school computer, you may need IT permission)
Optional: a router admin login if you want to block mining at the network level

Step-by-Step

Update your browser – Ensure you’re using the latest version of your browser. Updates often include security patches that help block malicious scripts.
Install a dedicated mining blocker extension – For Chrome, Edge, or Firefox, add a reputable extension like “No Coin” or “MinerBlock.” These extensions specifically detect and block cryptocurrency mining scripts. For Safari, look for “MinerBlock” or a similar content blocker.
Enable your browser’s built-in protections – In Chrome or Edge, go to Settings > Privacy and Security > Security and select “Standard” or “Strict” protection. In Firefox, go to Settings > Privacy & Security and set Enhanced Tracking Protection to “Strict.” These features block many known mining domains.
Use a reputable ad blocker – Many mining scripts are delivered through ads. Install uBlock Origin (available for all major browsers). It has a built-in filter list that blocks known mining domains. Make sure to enable the “uBlock filters – Cryptocurrency mining” list in the extension’s settings.
Disable JavaScript on untrusted sites – For sites you don’t trust, you can turn off JavaScript entirely. In Chrome, click the padlock icon next to the URL, go to Site settings, and set JavaScript to “Block.” In Firefox, click the shield icon and choose “Disable protection for now” – but for permanent blocking, use an extension like NoScript. This is a drastic step, but it’s effective.
Block mining domains at the network level – If you control your router, you can block known mining domains by adding them to a blacklist. Log into your router’s admin panel, find the “Parental Controls” or “Firewall” section, and add domains like coinhive.com (now defunct) and other known mining domains. For a more comprehensive approach, use a DNS service like NextDNS or OpenDNS that offers pre-made blocklists for cryptocurrency mining.
Use a browser that has built-in mining protection – The Brave browser automatically blocks known mining scripts and trackers. If you’re frequently targeted, switching to Brave can be a simple, permanent solution.

Common Mistakes

Only relying on one method – A single extension may not catch everything. Use a combination of an ad blocker, a mining-specific blocker, and browser protections.
Ignoring browser updates – Outdated browsers have known vulnerabilities that mining scripts exploit. Always keep your browser up to date.
Disabling protections on suspicious sites – Some sites ask you to disable your ad blocker to access content. Do not do this unless you absolutely trust the site, as it can open the door to mining scripts.
Assuming mobile browsers are safe – Mining scripts can run on mobile browsers too. Install a mobile ad blocker like AdGuard or use a privacy-focused browser like Brave on your phone.

Tips

Monitor your CPU usage – If your computer’s fan is running loudly or the system feels sluggish even when idle, check Task Manager (Windows) or Activity Monitor (Mac) to see if a browser tab is using high CPU. This is often a sign of mining.
Use a script blocker by default – Extensions like NoScript (Firefox) or ScriptSafe (Chrome) block all JavaScript by default, allowing you to whitelist only trusted sites. This gives you maximum control, but it can break some websites.
Clear your browser cache regularly – Some mining scripts are injected via cached files. Clearing your cache can remove them.
Consider a VPN with ad-blocking – Some VPN services include ad and malware blocking, which can also stop mining scripts before they reach your browser.

Troubleshooting

My CPU is still high after installing blockers – First, check if the high usage is from a browser tab. If so, close that tab. If the problem persists, try disabling all extensions to see if one is causing a conflict. Then re-enable them one by one.
The extension isn’t blocking anything – Make sure the extension is updated and its filters are enabled. Some extensions require you to manually enable the mining filter list in settings.
I can’t install extensions on my work computer – If you don’t have admin rights, use a portable browser like Firefox Portable on a USB drive, or use a browser with built-in protections like Brave (which doesn’t require extensions for basic blocking).
Websites break when I block JavaScript – If a site stops working, add it to your whitelist in NoScript or ScriptSafe. If you’re using a blanket JavaScript blocker, you’ll need to allow scripts from that site’s domain.
Mining still happens on my phone – Mobile browsers often have limited extension support. Use a dedicated mobile browser like Firefox with uBlock Origin, or use a DNS-based blocker like NextDNS.

Frequently Asked Questions

Is CPU mining illegal?
It’s not illegal in most places, but it’s unethical and often a violation of a website’s terms of service. It’s also a security risk because it’s usually done without your consent.

Can mining damage my computer?
Yes, prolonged high CPU usage can cause overheating, which may damage components over time. It also increases your electricity bill.

Why do websites mine cryptocurrency?
As an alternative to ads, some sites use mining to generate revenue. However, many do it without user consent, which is why it’s considered malicious.

Will these methods slow down my browsing?
Blocking scripts can sometimes cause pages to load slower because they have to load the script, then block it. However, the overall effect is usually a faster, more responsive browser because your CPU isn’t being used for mining.

Can I mine cryptocurrency myself to offset the risk?
You can, but it’s generally not profitable on consumer hardware. It’s better to simply block unwanted mining.

Do I need to worry about mining on my smart TV or other devices?
Yes, any device with a browser can be targeted. Use the same protections on your TV’s browser if it has one, or avoid browsing on such devices.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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