OJOSA

Thanks for the quick help!

I actually had two issues that were preventing this from working. One was as you suspected–I was pointing to /images/ instead of the applicable directory. I also had to remove the line root /home/www-data;.

My setup is quite different from the tutorial’s, and I’m just a casual user and am not well-versed in any of this, but in case it helps others:

1) I edited the mime.types file exactly as the tutorial suggests and added:

image/webp webp;

2) In my nginx.conf file, I included:

map $http_accept $webp_suffix {
default   "";
"~*webp" ".webp";
}

3) In included the last part in etc/nginx/sites-available/default (in my case, …/sites-available/wordpress) within the server block and also adjusted the try_files line. So this is what is working for me:

location ~* ^/wp-content/.+\.(png|jpg)$ {
        add_header Vary Accept;
	    try_files $uri$webp_suffix $uri/ =404;
    }

Also, I dunno if it would have made a difference or not, but before taking the above steps I apt-get install -ed imagemagick and webp to my server.