MRT Explained: the built-in malware scanner most Windows users don't know they have

If you're running Windows, there's a decent chance you already own a malware removal tool you've never opened. It's called MRT — the Malicious Software Removal Tool — and it ships with every modern version of Windows, sitting quietly in the background until you actually need it.

Most people have no idea it's there. Here's what it does, and how to put it to use.

What is MRT?

MRT is a lightweight scanning tool built directly into Windows. Unlike a full antivirus suite, it isn't designed for real-time protection — it doesn't sit in the background watching for threats as they happen. Instead, it's meant for on-demand scans: you run it, it checks your system against a list of known malicious software, and it removes anything it finds.

Because it's built into the OS, there's nothing to download or install. It's already on your machine.

How to run MRT

Getting MRT up and running takes seconds:

1. Press Win + R to open the Run dialog.
2. Type mrt (no quotes) and hit Enter.
3. When the tool opens, select Full Scan — the middle option.
4. Let it run. Depending on how much is on your drive, a full scan can take a while, so it's a good one to kick off when you're stepping away from your PC.

Once it finishes, MRT will report anything it found and remove it automatically.

MRT vs. Microsoft Safety Scanner

If you want something a bit more current, Microsoft also offers the Microsoft Safety Scanner, a close relative of MRT that uses the same underlying detection engine. The key difference is update frequency: MRT is refreshed periodically through Windows Update, while the Safety Scanner is updated far more often — which is exactly why Microsoft recommends downloading a fresh copy every time you want to run it, rather than reusing an old installer.

If MRT is your "it's already there" option, Safety Scanner is the "I want the latest definitions right now" option.

Should you rely on it as your only protection?

MRT is a solid tool for periodic checkups, but it isn't a replacement for real-time antivirus protection. It won't stop a threat as it arrives — it only cleans up what's already on your system when you run a scan. Pairing it with Windows Security (or another antivirus solution) running in the background, plus the occasional MRT or Safety Scanner sweep, is a reasonable, low-effort way to keep your system clean.

It's free, it's already installed, and it takes just a couple of clicks to run — there's little reason not to give it a spin every so often.