Unblock-File

Unblock-File
    [-Path] <String[]>
    [-WhatIf]
    [-Confirm]
    [<CommonParameters>]

Unblock-File
    -LiteralPath <String[]>
    [-WhatIf]
    [-Confirm]
    [<CommonParameters>]

The Unblock-File cmdlet lets you open files that were downloaded from the Internet. It unblocks PowerShell script files that were downloaded from the Internet so you can run them, even when the PowerShell execution policy is RemoteSigned. By default, these files are blocked to protect the computer from untrusted files.

Before using the Unblock-File cmdlet, review the file and its source and verify that it is safe to open.

Internally, the Unblock-File cmdlet removes the Zone.Identifier alternate data stream, which has a value of "3" to indicate that it was downloaded from the Internet.

For more information about PowerShell execution policies, see about_Execution_Policies.

This cmdlet was introduced in Windows PowerShell 3.0.

PS C:\> Unblock-File -Path C:\Users\User01\Documents\Downloads\PowerShellTips.chm

This command unblocks the PowerShellTips.chm file.

PS C:\> dir C:\Downloads\*PowerShell* | Unblock-File

This command unblocks all of the files in the C:\Downloads directory whose names include "PowerShell". Do not run a command like this one until you have verified that all files are safe.

The first command uses the *Stream* parameter of the Get-Item cmdlet get files with the Zone.Identifier stream.Although you could pipe the output directly to the **Unblock-File** cmdlet (Get-Item * -Stream "Zone.Identifier" -ErrorAction SilentlyContinue | ForEach {Unblock-File $_.FileName}), it is prudent to review the file and confirm that it is safe before unblocking.
PS C:\> Get-Item * -Stream "Zone.Identifier" -ErrorAction SilentlyContinue
   FileName: C:\ps-test\Start-ActivityTracker.ps1

Stream                   Length
------                   ------
Zone.Identifier              26

The second command shows what happens when you run a blocked script in a PowerShell session in which the execution policy is **RemoteSigned**. The RemoteSigned policy prevents you from running scripts that are downloaded from the Internet unless they are digitally signed.
PS C:\> C:\ps-test\Start-ActivityTracker.ps1
c:\ps-test\Start-ActivityTracker.ps1 : File c:\ps-test\Start-ActivityTracker.ps1 cannot
be loaded. The file c:\ps-test\Start-ActivityTracker.ps1 is not digitally signed. The script
will not execute on the system. For more information, see about_Execution_Policies.

At line:1 char:1
+ c:\ps-test\Start-ActivityTracker.ps1
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : SecurityError: (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess

The third command uses the **Unblock-File** cmdlet to unblock the script so it can run in the session.
PS C:\> Get-Item C:\ps-test\Start-ActivityTracker.ps1 | Unblock-File

This command shows how to find and unblock PowerShell scripts.

This cmdlet supports the common parameters: -Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutBuffer, -OutVariable, -PipelineVariable, -ProgressAction, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters.

You can pipe a file path to Unblock-File.

This cmdlet does not generate any output.

• The Unblock-File cmdlet works only in file system drives.
• Unblock-File performs the same operation as the Unblock button on the Properties dialog box in File Explorer.
• If you use the Unblock-File cmdlet on a file that is not blocked, the command has no effect on the unblocked file and the cmdlet does not generate errors.