PowerShell – Get Text Encoding Type

function Get-Encoding
{
  param
  (
    [Parameter(Mandatory,ValueFromPipeline,ValueFromPipelineByPropertyName)]
    [Alias('FullName')]
    [string]
    $Path
  )

  process 
  {
    $bom = New-Object -TypeName System.Byte[](4)
        
    $file = New-Object System.IO.FileStream($Path, 'Open', 'Read')
    
    $null = $file.Read($bom,0,4)
    $file.Close()
    $file.Dispose()
    
    $enc = [Text.Encoding]::ASCII
    if ($bom[0] -eq 0x2b -and $bom[1] -eq 0x2f -and $bom[2] -eq 0x76) 
      { $enc =  [Text.Encoding]::UTF7 }
    if ($bom[0] -eq 0xff -and $bom[1] -eq 0xfe) 
      { $enc =  [Text.Encoding]::Unicode }
    if ($bom[0] -eq 0xfe -and $bom[1] -eq 0xff) 
      { $enc =  [Text.Encoding]::BigEndianUnicode }
    if ($bom[0] -eq 0x00 -and $bom[1] -eq 0x00 -and $bom[2] -eq 0xfe -and $bom[3] -eq 0xff) 
      { $enc =  [Text.Encoding]::UTF32}
    if ($bom[0] -eq 0xef -and $bom[1] -eq 0xbb -and $bom[2] -eq 0xbf) 
      { $enc =  [Text.Encoding]::UTF8}
        
    [PSCustomObject]@{
      Encoding = $enc
      Path = $Path
    }
  }
}

Get-Encoding ~\Desktop\text.txt

Reference: https://community.idera.com/database-tools/powershell/powertips/b/tips/posts/get-text-file-encoding