If you have ever pressed Windows and R, typed a strange little word, and seen a security window pop up, you may have met the Microsoft Malicious Software Removal Tool without even knowing it. It is one of the most quietly useful safety tools hiding inside your PC, and most people have no idea it is there. As Microsoft explains in its official guide, it helps keep Windows free from common malware. This guide breaks down what it is, whether you should run it, and exactly how to use it on Windows 10 and 11, in plain, simple steps with pictures.
| The Short Version The Microsoft Malicious Software Removal Tool (MSRT) is a free, built-in Windows utility that finds and removes a small list of very common malware. It is NOT a full antivirus and does NOT protect you in real time. Good news for beginners: Windows already runs it automatically in the background about once a month, so you usually do not need to do anything. You can run it by hand as a quick second opinion if you think your PC is infected. |
What Is the Microsoft Malicious Software Removal Tool
Let us start with the basics, in plain words. The Microsoft Malicious Software Removal Tool, often shortened to MSRT, is a small, free program that comes built into Windows. Its one job is to scan your computer for a specific list of common, dangerous malware and clean up any of it that it finds.
Microsoft first released it way back in January 2005, and it has quietly shipped with Windows ever since. The program file is named MRT.exe, which is why some people call the tool MRT for short. It lives in a system folder on your PC, and you almost never see it, because it usually does its work silently in the background.
| The Big Picture Think of MSRT as a cleanup crew, not a security guard. It does not stand at the door stopping threats. Instead, it sweeps through once in a while to remove a few specific, nasty pests if they got inside. | |||
| Quick Fact | Detail | ||
| Full name | Windows Malicious Software Removal Tool (MSRT) | ||
| Program file | MRT.exe | ||
| Cost | Completely free, built into Windows | ||
| First released | January 2005 | ||
| Works on | Windows 11, Windows 10, and older versions | ||
| What it is | A cleanup tool for common malware, not an antivirus | ||
What It Does, and What It Does Not Do
This is the part that trips people up, so let us make it crystal clear. MSRT is powerful, but it is also very limited on purpose. Knowing the difference will save you a lot of confusion.
What It Does
- Removes common malware: it targets a small, carefully chosen list of the most widespread viruses, worms, and Trojans.
- Cleans up after an infection: it removes threats that are already on your PC and undoes some of the damage they caused.
- Runs automatically: Windows Update quietly runs it in the background about once a month.
What It Does Not Do
- No real-time protection: it does not watch your PC all day or block threats as they arrive. It only checks when it runs.
- Not a full antivirus: it only knows a small subset of all malware, not the millions of threats a real antivirus covers.
- Ignores some junk: it does not remove spyware, adware, browser toolbars, or annoying unwanted programs.
| Heads Up Because MSRT only looks for a short list of threats, a clean result does not prove your PC is totally malware-free. It just means none of those specific common threats were found. Always keep a real antivirus running too. |
MSRT vs Microsoft Defender: What’s the Difference
Many beginners mix these two up, so here is the simple version. Windows 10 and 11 already include a full, free antivirus called Microsoft Defender. MSRT is a completely separate, smaller tool. They work together, but they are not the same thing.
| Microsoft Defender | MSRT | |
| What it is | Full antivirus | Cleanup tool |
| Protection | Real-time, always on | Only when it runs |
| Covers | Almost all malware | A few common threats |
| Runs | Constantly in background | About once a month |
| Needed? | Yes, essential | Helpful extra |
| Why It Matters Microsoft Defender is your security guard, on duty 24 hours a day. MSRT is the once-a-month cleanup crew. You need the guard. The cleanup crew is a nice bonus that runs on its own. |
Should You Run It? (The Honest Answer)
Here is the straight answer most guides will not give you: for most people, you do not need to run MSRT by hand at all. As long as Windows Update is turned on, which it is by default, MSRT already runs by itself every month. You are covered without lifting a finger.
That said, there are a few good reasons to run it manually for a quick check:
- Your PC is acting strange: random crashes, pop-ups, slowdowns, or your browser keeps redirecting.
- You think you caught something: you clicked a bad link or opened a suspicious file and want a quick scan.
- You want a second opinion: a quick extra check alongside your main antivirus, just for peace of mind.
- You are cleaning up a PC: before handing a computer to someone else, for example.
| In Short If your PC is running fine, you can happily ignore MSRT and let it do its monthly thing. If something feels off, running it by hand takes two minutes and is completely safe. It is free and it will not harm your computer. |
The 3 Scan Types Explained
When you run MSRT yourself, it offers three choices. Here is what each one means in plain language, so you can pick with confidence.
| Scan Type | What It Checks | How Long |
| Quick scan | The areas where malware usually hides. Microsoft recommends this one. | A few minutes |
| Full scan | Every file on all your drives. Very thorough. | Up to a few hours |
| Customized scan | A quick scan plus one folder you choose. | A few minutes plus |
| Quick Tip Start with the Quick scan. It is the default, it is fast, and it checks the spots where threats usually hide. Only run a Full scan if the Quick scan finds something or you have a strong reason to dig deeper. |
How to Run the Tool on Windows 10 and 11: Step by Step
Good news: the steps are exactly the same on Windows 10 and Windows 11. Follow along with the pictures. The whole thing takes about two minutes for a Quick scan. We will use the fastest method, the Run box.
Step 1: Open the Run Box and Type mrt
Press the Windows key + R on your keyboard at the same time. A small box called Run will pop up in the bottom-left corner of your screen. In that box, type the three letters mrt and then press Enter (or click OK).
Step 2: Click Yes on the Permission Pop-up
Windows will ask for permission with a window titled User Account Control. It says something like “Do you want to allow this app to make changes to your device?” This is normal and safe. Click Yes to continue.
Step 3: Read the Welcome Screen and Click Next
The tool opens with a welcome screen titled “Microsoft Windows Malicious Software Removal Tool.” It explains in a few lines what the tool does. There is nothing to change here. Just click Next in the bottom-right corner.
Step 4: Choose Quick Scan and Click Next
Now you will see the three scan options: Quick scan, Full scan, and Customized scan. Quick scan is already selected for you, and it is the right choice for almost everyone. Leave it selected and click Next to start.
Step 5: Wait While It Scans
The tool now scans your PC. You will see a progress bar and the names of files flashing by as it checks them. A Quick scan usually takes just a few minutes. You can keep using your PC while it works, though it may feel a little slower. Let it finish.
Step 6: Read Your Results and Click Finish
When the scan finishes, you get a results screen. For most people it will say “No malicious software was detected.” That is exactly what you want to see. To see more detail, you can click View detailed results of the scan. When you are done, click Finish.
| The Cool Part That is the entire process. Six clicks and a couple of minutes. There is nothing to install and nothing to set up, the tool is already on your PC, ready whenever you want a quick check. |
Another Easy Way: Windows Search
Prefer not to use the Run box? You can open the exact same tool from the search bar. Click the Start button or the search box, type mrt, and click the result that appears. Click Yes on the permission prompt, and you will land on the same welcome screen from Step 3. Everything after that is identical.
Tip: Download the Newest Version First
The copy of MSRT already on your PC might be a month or two old. Since malware changes constantly, it is smart to grab the very latest version before a manual scan. You can download it free from the official Microsoft Download Center. Pick the 64-bit version if you are unsure, since nearly all modern PCs (and all Windows 11 PCs) are 64-bit. The downloaded file opens the very same wizard, no installation needed.
| Worth Knowing Microsoft refreshes MSRT about once a month, usually on the second Tuesday (often called Patch Tuesday). If your downloaded copy gets too old, the tool itself will gently suggest you grab a newer one. |
What If It Actually Finds Malware?
Most of the time you will see the all-clear message. But if MSRT does find something, do not panic. It will try to remove the threat automatically and tell you what it found. Here is your simple game plan:
- Let it clean up. Allow the tool to remove what it found. If it asks you to run a Full scan, say yes.
- Restart your PC if it asks you to. Some cleanups only finish after a reboot.
- Run a full Microsoft Defender scan. Open Windows Security, go to Virus and threat protection, choose Scan options, pick Full scan, and run it.
- Get a second opinion. Because MSRT only covers a few threats, run a trusted scanner like Malwarebytes or Microsoft Safety Scanner to be thorough.
| Heads Up A clean MSRT result is reassuring, but it is not the final word. MSRT only checks a short list of threats, so always follow up with a full antivirus scan if you genuinely suspect an infection. |
Where to See the Detailed Log
Every time MSRT runs, it saves a detailed report to a log file. Curious or want proof of a clean scan? You can open it. Press Windows key + R, type the line below, and press Enter. The file mrt.log will open in Notepad.
%systemroot%\debug\mrt.log
The full path is C:\Windows\debug\mrt.log. Inside, you will see the tool version, the date, and the results. For a clean scan, look for the line that reads “Results Summary: No infection found” and “Return code: 0.” That zero is the good news code that means nothing bad was found.
| Good to Know You might notice the scan counting several infections while it runs, then reporting none at the end. Do not worry, this is normal. MSRT flags possible suspects during the scan, then double-checks them and clears the harmless ones before showing the final result. The final result is the one that counts. |
Is mrt.exe a Virus? (A Common Worry)
If you spotted mrt.exe running on your PC and got nervous, relax. The real MSRT is a legitimate, safe Microsoft program. It lives in this exact folder:
C:\Windows\System32\MRT.exe
As long as the file sits in that System32 folder, it is the genuine, trusted tool, and you should not delete it. Windows would just put it back anyway. The only time to be suspicious is if you find a file named mrt.exe somewhere else entirely, like in your Downloads or a random folder. In that case, scan it with your antivirus to be safe.
The Microsoft Malicious Software Removal Tool is a handy little safety net that has quietly lived inside Windows for two decades. It is free, it is safe, and it removes some of the most common malware out there, all on its own, about once a month. For most people, the best move is simply to leave Windows Update on and let it do its job. If your PC ever feels off, running it by hand is a quick, two-minute check that costs nothing. Just remember the golden rule: MSRT is a helpful sidekick, not a replacement for a real antivirus like Microsoft Defender. Keep that running, and you are in good shape. For the official details, see Microsoft’s support page.
Frequently Asked Questions
Is MSRT the Same as Windows Defender
No. Microsoft Defender is a full, always-on antivirus that protects you in real time. MSRT is a smaller, separate cleanup tool that only checks for a few common threats when it runs. You need Defender; MSRT is a helpful extra.
Do I Need to Run MSRT If I Have Antivirus
Not really. MSRT is a complement, not a requirement, and it already runs automatically once a month through Windows Update. It can be handy as a quick second opinion, but your real antivirus does the heavy lifting.
Is It Safe to Run
Yes. MSRT is a legitimate, free Microsoft tool that is digitally signed and will not harm your PC. The only minor caveat is that cleaning a deeply infected file can occasionally cause some data loss, which is unavoidable with any malware removal.
Does MSRT Run Automatically
Yes. As long as Windows Update is on (the default), MSRT runs quietly in the background about once a month. You only see it if it finds something or if you open it yourself.
Is It Safe to Delete mrt.exe
Do not delete the copy in C:\Windows\System32, it is legitimate and Windows will restore it anyway. Only be cautious about a file named mrt.exe found outside that folder, which could be an impostor worth scanning.
Does MSRT Slow Down My PC
Only a little, and only while it is actively scanning. A Quick scan is light and brief. A Full scan uses more power and can slow things down for a while, so run it when you are not busy.
Is MSRT Enough to Protect Me on Its Own
No. MSRT only removes a small list of common threats and gives no real-time protection. You still need a full antivirus like Microsoft Defender running at all times.
