How do you comment out code in PowerShell?

In PowerShell V1 there's only # to make the text after it a comment.

# This is a comment in PowerShell

In PowerShell V2 <# #> can be used for block comments and more specifically for help comments.

#REQUIRES -Version 2.0

<#
.SYNOPSIS
    A brief description of the function or script. This keyword can be used
    only once in each topic.
.DESCRIPTION
    A detailed description of the function or script. This keyword can be
    used only once in each topic.
.NOTES
    File Name      : xxxx.ps1
    Author         : J.P. Blanc (jean-paul_blanc@silogix-fr.com)
    Prerequisite   : PowerShell V2 over Vista and upper.
    Copyright 2011 - Jean Paul Blanc/Silogix
.LINK
    Script posted over:
    http://silogix.fr
.EXAMPLE
    Example 1
.EXAMPLE
    Example 2
#>
Function blabla
{}

For more explanation about .SYNOPSIS and .* see about_Comment_Based_Help.

Remark: These function comments are used by the Get-Help CmdLet and can be put before the keyword Function, or inside the {} before or after the code itself.

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You use the hash mark like this:

# This is a comment in PowerShell

Wikipedia has a good page for keeping track of how to do comments in several popular languages:

Comments

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Single line comments start with a hash symbol, everything to the right of the # will be ignored:

# Comment Here

In PowerShell 2.0 and above multi-line block comments can be used:

<# 
  Multi 
  Line 
#> 

You could use block comments to embed comment text within a command:

Get-Content -Path <# configuration file #> C:\config.ini

Note: Because PowerShell supports Tab Completion you need to be careful about copying and pasting Space + TAB before comments.

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It's the #.

See PowerShell - Special Characters And Tokens for special characters.

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Within PowerShell ISE you can hit Ctrl+J to open the Start Snipping menu and select Comment block:

https://i.stack.imgur.com/caJt2.png

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Here

# Single line comment in PowerShell

<#
--------------------------------------
Multi-line comment in PowerShell V2+
--------------------------------------
#>

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Use a hashtag followed by a white space(!) for this:

 # Comment here

Do not forget the white space here! Otherwise it can interfere with internal commands.

E.g., this is not a comment:

#requires -runasadmin

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You can make:

 (Some basic code) # Use "#" after a line and use:

 <#
    for more lines
    ...
    ...
    ...
    ..
    .
 #>

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There is a special way of inserting comments add the end of script:

....
exit 

Hi
Hello
We are comments
And not executed 

Anything after exit is not executed, and behave quite like comments.

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I'm a little bit late to this party but seems that nobody actually wrote all use cases. So...

Only supported version of PowerShell these days (fall of 2020 and beyond) are:

Windows PowerShell 5.1.x

PowerShell 7.0.x.

You don't want to or you shouldn't work with different versions of PowerShell.

Both versions (or any another version which you could come around WPS 3.0-5.0, PS Core 6.x.x on some outdated stations) share the same comment functionality.

One line comments

# Get all Windows Service processes <-- one line comment, it starts with '#'
Get-Process -Name *host*

Get-Process -Name *host* ## You could put as many ### as you want, it does not matter

Get-Process -Name *host* # | Stop-Service # Everything from the first # until end of the line is treated as comment

Stop-Service -DisplayName Windows*Update # -WhatIf # You can use it to comment out cmdlet switches

Multi line comments

<#
Everyting between '< #' and '# >' is
treated as a comment. A typical use case is for help, see below.

# You could also have a single line comment inside the multi line comment block.
# Or two... :)

#>

<#
.SYNOPSIS
    A brief description of the function or script.
    This keyword can be used only once in each topic.

.DESCRIPTION
    A detailed description of the function or script.
    This keyword can be used only once in each topic.

.NOTES
    Some additional notes. This keyword can be used only once in each topic.
    This keyword can be used only once in each topic.

.LINK
    A link used when Get-Help with a switch -OnLine is used.
    This keyword can be used only once in each topic.

.EXAMPLE
    Example 1
    You can use this keyword as many as you want.

.EXAMPLE
    Example 2
    You can use this keyword as many as you want.
#>

Nested multi line comments

<#
Nope, these are not allowed in PowerShell.

<# This will break your first multiline comment block... #>
...and this will throw a syntax error.
#>

In code nested multi line comments

<#
The multi line comment opening/close
can be also used to comment some nested code
or as an explanation for multi chained operations..
#>
Get-Service | <# Step explanation #>
Where-Object { $_.Status -eq [ServiceProcess.ServiceControllerStatus]::Stopped } |
<# Format-Table -Property DisplayName, Status -AutoSize |#>
Out-File -FilePath Services.txt -Encoding Unicode

Edge case scenario

# Some well written script
exit
Writing something after exit is possible but not recommended.
It isn't a comment.
Especially in Visual Studio Code, these words baffle PSScriptAnalyzer.
You could actively break your session in VS Code.

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