Powershell remove HTML tags in string content

Question

I have a large HTML data string separated into small chunks. I am trying to write a PowerShell script to remove all the HTML tags, but am finding it difficult to find the right regex pattern.

Example String:

<p>This is an example<br />of various <span style="color: #445444">html content</span>

I have tried using:

$string -replace '\<([^\)]+)\>',''

It works with simple examples but ones such as above it captures the whole string.

Any suggestions on whats the best way to achieve this?

Answer 1

To resolve umlauts and special characters I used a html Object. Here is my function:

Function ConvertFrom-Html
{
    <#
        .SYNOPSIS
            Converts a HTML-String to plaintext.

        .DESCRIPTION
            Creates a HtmlObject Com object und uses innerText to get plaintext. 
            If that makes an error it replaces several HTML-SpecialChar-Placeholders and removes all <>-Tags via RegEx.

        .INPUTS
            String. HTML als String

        .OUTPUTS
            String. HTML-Text als Plaintext

        .EXAMPLE
        $html = "<p><strong>Nutzen:</strong></p><p>Der&nbsp;Nutzen ist &uuml;beraus gro&szlig;.<br />Test ob 3 &lt; als 5 &amp; &quot;4&quot; &gt; &apos;2&apos; it?"
        ConvertFrom-Html -Html $html
        $html | ConvertFrom-Html

        Result:
        "Nutzen:
        Der Nutzen ist überaus groß.
        Test ob 3 < als 5 ist & "4" > '2'?"


        .Notes
            Author: Ludwig Fichtinger FILU
            Inital Creation Date: 01.06.2021
            ChangeLog: v2 20.08.2021 try catch with replace for systems without Internet Explorer

    #>

    [CmdletBinding(SupportsShouldProcess = $True)]
    Param(
        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true, HelpMessage = "HTML als String")]
        [AllowEmptyString()]
        [string]$Html
    )

    try
    {
        $HtmlObject = New-Object -Com "HTMLFile"
        $HtmlObject.IHTMLDocument2_write($Html)
        $PlainText = $HtmlObject.documentElement.innerText
    }
    catch
    {
        $nl = [System.Environment]::NewLine
        $PlainText = $Html -replace '<br>',$nl
        $PlainText = $PlainText -replace '<br/>',$nl
        $PlainText = $PlainText -replace '<br />',$nl
        $PlainText = $PlainText -replace '</p>',$nl
        $PlainText = $PlainText -replace '&nbsp;',' '
        $PlainText = $PlainText -replace '&Auml;','Ä'
        $PlainText = $PlainText -replace '&auml;','ä'
        $PlainText = $PlainText -replace '&Ouml;','Ö'
        $PlainText = $PlainText -replace '&ouml;','ö'
        $PlainText = $PlainText -replace '&Uuml;','Ü'
        $PlainText = $PlainText -replace '&uuml;','ü'
        $PlainText = $PlainText -replace '&szlig;','ß'
        $PlainText = $PlainText -replace '&amp;','&'
        $PlainText = $PlainText -replace '&quot;','"'
        $PlainText = $PlainText -replace '&apos;',"'"
        $PlainText = $PlainText -replace '<.*?>',''
        $PlainText = $PlainText -replace '&gt;','>'
        $PlainText = $PlainText -replace '&lt;','<'
    }

    return $PlainText
}

Example:

"<p><strong>Nutzen:</strong></p><p>Der&nbsp;Nutzen ist &uuml;beraus gro&szlig;.<br />Test ob 3 &lt; als 5 ist &amp; &quot;4&quot; &gt; &apos;2&apos;?" | ConvertFrom-Html

Result:

Nutzen:
Der Nutzen ist überaus groß.
Test ob 3 < als 5 ist & "4" > '2'?

Answer 2

For a pure regex, it should be as easy as <[^>]+>:

$string -replace '<[^>]+>',''

Debuggex Demo

Note that this could fail with certain HTML comments or the contents of <pre> tags.

Instead, you could use the HTML Agility Pack (alternative link), which is designed for use in .Net code, and I've used it successfully in PowerShell before:

Add-Type -Path 'C:\packages\HtmlAgilityPack.1.4.6\lib\Net40-client\HtmlAgilityPack.dll'

$doc = New-Object HtmlAgilityPack.HtmlDocument
$doc.LoadHtml($string)
$doc.DocumentNode.InnerText

HTML Agility Pack works well with non-perfect HTML.

Answer 3

You can try this:

$string -replace '<.*?>',''