IIS compatibility?

Hi @joben ,

Thank you for your message. I have to admit that we didn’t do tests on IIS.

Are you able to get the rules from the .htaccess file and use them in the configuration?

Hi Mateusz and thanks for the reply!

I actually never found that any .htaccess file was created, but I found an existing IIS URL Rewrite rule on some random website that I modified slightly, and it actually worked as intended after I generated the webp files. It served me webp files in Chrome and regular files in Edge.

However, a few of the png images and jpg images didn’t get converted. I compared the original folder with the destination folder so I know that some of the webp images do not exist. I havn’t found any logs or debug messages from the generation process so I still don’t know what’s wrong.

Here is the current IIS Rewrite rule that I am using:

<rule name="Webp1" enabled="true" stopProcessing="true">
    <match url=".*wp-content/uploads.*/([0-9]*)/([0-9]*)/(.*_.*)(\.jpg|\.jpeg|\.png)" />
    <conditions logicalGrouping="MatchAny">
                        <add input="{HTTP_ACCEPT}" pattern="\bimage/webp\b" />
    </conditions>
    <action type="Rewrite" url="/wp-content/uploads-webpc/{R:1}/{R:2}/{R:3}{R:4}.webp" logRewrittenUrl="false" />
</rule>

Here you can find all the rules that occur in the .htaccess file:

# BEGIN WebP Converter
<IfModule mod_mime.c>
  AddType image/webp .webp
</IfModule>
<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{HTTP_ACCEPT} image/webp
  RewriteCond %{DOCUMENT_ROOT}/wp-content/uploads-webpc/$1.jpg.webp -f
  RewriteRule wp-content/uploads/(.+)\.jpg$ wp-content/uploads-webpc/$1.jpg.webp [T=image/webp]
  RewriteCond %{HTTP_ACCEPT} image/webp
  RewriteCond %{DOCUMENT_ROOT}/wp-content/uploads-webpc/$1.jpeg.webp -f
  RewriteRule wp-content/uploads/(.+)\.jpeg$ wp-content/uploads-webpc/$1.jpeg.webp [T=image/webp]
  RewriteCond %{HTTP_ACCEPT} image/webp
  RewriteCond %{DOCUMENT_ROOT}/wp-content/uploads-webpc/$1.png.webp -f
  RewriteRule wp-content/uploads/(.+)\.png$ wp-content/uploads-webpc/$1.png.webp [T=image/webp]
</IfModule>
<IfModule mod_expires.c>
  ExpiresActive On
  ExpiresByType image/webp "access plus 1 year"
</IfModule>
# END WebP Converter

I tried importing the rules in IIS but it failed because the T= flag is not recognized.
I removed the T flags but the rules are not working properly.

I think what is needed for this to work in IIS is one of these things:

Option 1: Troubleshoot the converter why some images are not converted and use the rule that I posted.
Option 2: Write an IIS rule that loads the webp image only if it exists, if it doesnt, load the original jpeg/png version.

I lack the necessary skills to make it work, but if anyone wants me to test something or debug in an IIS environment I am happy to help.

Thank you for your help and time, I appreciate very much.

T flag is required for this plugin to work. This is what its “magic” is all about, ie redirects to WebP files that do not change the URL.