Encoding converts data from one representation to another so it can be safely stored, transmitted, or processed. Decoding reverses that process. PowerShell has built-in support for several common encoding schemes.

Base64

Base64 encodes binary data as printable ASCII text. It is widely used for embedding files in text formats, sending data in HTTP headers, and PowerShell’s own -EncodedCommand parameter.

Encoding a String

$text = "Hello, World!"
$bytes = [System.Text.Encoding]::UTF8.GetBytes($text)
$encoded = [System.Convert]::ToBase64String($bytes)
$encoded

Result:

SGVsbG8sIFdvcmxkIQ==

Decoding a String

$encoded = "SGVsbG8sIFdvcmxkIQ=="
$bytes = [System.Convert]::FromBase64String($encoded)
$decoded = [System.Text.Encoding]::UTF8.GetString($bytes)
$decoded

Result:

Hello, World!

Encoding a File

$bytes = [System.IO.File]::ReadAllBytes("C:\Temp\image.png")
$encoded = [System.Convert]::ToBase64String($bytes)
$encoded | Set-Content -Path "C:\Temp\image.b64"

Decoding a File

$encoded = Get-Content -Path "C:\Temp\image.b64" -Raw
$bytes = [System.Convert]::FromBase64String($encoded)
[System.IO.File]::WriteAllBytes("C:\Temp\image-restored.png", $bytes)

EncodedCommand

PowerShell’s -EncodedCommand parameter accepts a Base64-encoded command, which is useful for passing complex scripts as a single-line argument (e.g. from a scheduler or another process). Note that -EncodedCommand requires UTF-16LE encoding, not UTF-8.

$command = 'Write-Host "Hello from encoded command"'
$bytes   = [System.Text.Encoding]::Unicode.GetBytes($command)
$encoded = [System.Convert]::ToBase64String($bytes)

# Run it
powershell.exe -EncodedCommand $encoded

Result:

Hello from encoded command

URL Encoding

URL encoding (percent-encoding) replaces characters that are not allowed in a URL with a % followed by their hex value. PowerShell can do this via the System.Net.WebUtility class or System.Uri.

Encoding a URL String

$text    = "hello world & more=stuff"
$encoded = [System.Net.WebUtility]::UrlEncode($text)
$encoded

Result:

hello+world+%26+more%3Dstuff

Decoding a URL String

$encoded = "hello+world+%26+more%3Dstuff"
$decoded = [System.Net.WebUtility]::UrlDecode($encoded)
$decoded

Result:

hello world & more=stuff

URI Encoding (RFC 3986)

System.Uri::EscapeDataString follows RFC 3986 and is preferred when building query strings for REST APIs, as it encodes spaces as %20 rather than +.

$text    = "hello world & more=stuff"
$encoded = [System.Uri]::EscapeDataString($text)
$encoded

$decoded = [System.Uri]::UnescapeDataString($encoded)
$decoded

Result:

hello%20world%20%26%20more%3Dstuff
hello world & more=stuff

HTML Encoding

HTML encoding replaces characters such as <, >, and & with their HTML entity equivalents, preventing them from being interpreted as markup.

Encoding HTML

$text    = '<script>alert("XSS")</script> & other <stuff>'
$encoded = [System.Net.WebUtility]::HtmlEncode($text)
$encoded

Result:

<script>alert("XSS")</script> & other <stuff>

Decoding HTML

$encoded = "<b>Hello</b> & welcome"
$decoded = [System.Net.WebUtility]::HtmlDecode($encoded)
$decoded

Result:

<b>Hello</b> & welcome

Character Encoding

Character encoding determines how text is represented as bytes. This is especially important when reading and writing files. See the Reading Files and Writing Files pages for file I/O examples.

Common Encodings in PowerShell

# List available encoding names
[System.Text.Encoding]::GetEncodings() | Select-Object -Property Name, DisplayName

The most common encodings you will encounter:

Writing a File with a Specific Encoding

# UTF-8 without BOM (common for cross-platform files)
$content = "Héllo Wörld"
[System.IO.File]::WriteAllText("C:\Temp\output.txt", $content, [System.Text.Encoding]::UTF8)

# UTF-8 with BOM (Windows default)
$content | Out-File -FilePath "C:\Temp\output-bom.txt" -Encoding utf8BOM

Reading a File with a Specific Encoding

# Explicitly specify encoding when reading
$content = Get-Content -Path "C:\Temp\output.txt" -Encoding UTF8
$content

Summary