4 Ways to Update Windows Security Signatures Manually

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Update Windows Security if your computer doesn't do it automatically

Co-authored by Hannah Dillon Reviewed by Stan Kats

Last Updated: August 21, 2026 Fact Checked

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Using Windows Security

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Using PowerShell

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Using Command Prompt

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Manual Install

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Normally, Windows Security will install its own updates. But if your computer has been offline for a while, you have slow or unstable internet, you're on a corporate or school network, or your PC is permanently offline, you may miss updates. In this article, we'll go over four easy ways you can manually install Windows Security signature updates. Keep reading to learn how.

Ways to Update Windows Security Signatures Manually

Open the Windows Security dashboard and click Virus & threat protection > Protection updates > Check for updates.
Open an elevated PowerShell and run the command "Update-MpSignature."
Open an elevated Command Prompt and run the commands "cd %ProgramFiles%\Windows Defender," "MpCmdRun.exe -removedefinitions -dynamicsignatures," and "MpCmdRun.exe -SignatureUpdate."
Download the update from Microsoft and run the EXE file to install it.

Method 1

Method 1 of 4:

Using Windows Security

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The easiest way to do this is to type windows security into the taskbar search bar, then click Windows Security in the Start menu that pops up.
2
Click Virus & threat protection. All menu options are arranged in a grid, and this is the first option in the upper-left corner. It has a shield icon. If everything is good with your system, the icon will also show a green check mark.

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3
Click Protection updates. It's under the "Virus & threat protection updates" header. You may need to scroll down slightly to find this option.
- Under this header, you'll also see the last time your security signatures were updated. If the date is recent, you may not need to do a manual update.
4
Click Check for updates. It's under the "Security intelligence" header. If there's a pending update, it will be installed.^{[1]
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Method 2

Method 2 of 4:

Using PowerShell

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1
Open PowerShell as an administrator. The easiest way to do this is to type powershell into the taskbar search bar and right-click Windows PowerShell in the Start menu that appears, then click Run as administrator.
- Note that you must be connected to the internet to complete this method.
2
Type Update-MpSignature. Press ↵ Enter to run the command. You won't see a progress bar, but after a few moments, you'll be able to type in PowerShell again. Your security signatures will be updated after this.^{[2]
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Method 3

Method 3 of 4:

Using Command Prompt

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1
Open Command Prompt as an administrator. The easiest way to do this is to type command prompt into the taskbar search bar, right-click on Command Prompt in the Start menu, and then click Run as administrator.
- Note that you must be connected to the internet to complete this method.
2
Change your directory. In Command Prompt, copy and paste the command cd %ProgramFiles%\Windows Defender and press ↵ Enter. This will change your directory to the Windows Defender folder.
3
Run the command to remove certain downloaded updates. This prepares Defender for the security signatures you're going to have it download. Copy and paste MpCmdRun.exe -removedefinitions -dynamicsignatures into Command Prompt and press ↵ Enter.
4
Run the update command. Copy and paste the command MpCmdRun.exe -SignatureUpdate into Command Prompt and press ↵ Enter. This will download and install the latest security signature updates to Defender.

Method 4

Method 4 of 4:

Manual Install

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1
Download the security signature update for your operating system. Go to the Windows Security Defender updates page and scroll down to the "Manually download the update" section. Under this section, you'll find a table with the latest Defender updates. The link you'll want to click is in the first line, next to "Microsoft Defender Antivirus for Windows 11, Windows 10, Windows 8.1, and Windows Server."
- Alternatively, click these links to directly download the update:
  - 32-bit
  - 64-bit
  - ARM
    - To see whether you have a 32-bit, a 64-bit, or an ARM-based version of Windows, go to Settings > System > About.
- This method can be completed offline, but you'll need a computer with internet access to download the update.
2
Double-click the EXE file you downloaded. This program will update your Windows Security signatures.^{[3]
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- If you want to update an offline PC, you'll need to transfer the EXE file over using a flash drive.^{[4]
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