The best free mp4 to mp3 converter that still works in 2025?

Windows PowerShell itself does not include built-in MP4 to MP3 converter in Windows 11 or Windows 10. However, you can automate conversion tasks using PowerShell in combination with:

1. Windows Media Foundation (WMF)
2. COM objects like Windows Media Player

There is no fully native PowerShell-only method that supports decoding and re-encoding MP4 to MP3 without invoking outside libraries or tools. But here’s a commonly used workaround:

$inputFolder = "C:\Videos"
$outputFolder = "C:\Audio"

# Create output folder if it doesn't exist
if (!(Test-Path $outputFolder)) {
    New-Item -ItemType Directory -Path $outputFolder
}

# Convert all .mp4 files in the input folder
Get-ChildItem -Path $inputFolder -Filter *.mp4 | ForEach-Object {
    $inputFile = $_.FullName
    $outputFile = Join-Path $outputFolder ($_.BaseName + ".mp3")
    Start-Process -NoNewWindow -FilePath "ffbmpeg" -ArgumentList "-i `"$inputFile`" -vn -ab 192k `"$outputFile`"" -Wait
}

✅ This script:

Converts all MP4 files in a folder to MP3.

Uses FFbmpeg in the background.

Works well for batch conversion.