Just doing some checks on my site (farfromready.com) using stuff like Google PageSpeed Insights or GTmetrix, and bth are heavily advising me to serve scaled images on the main page, for the thumbnails of my blog, as apparently the site is serving them resized by html or css instead of just scaled images, which could help me halve my site’s size. I cannot manage to find a plugin that does that, and I have no idea about the necessary coding. I’m a bit clueless here, could anyone help me please?
Sadly that doesn’t seem to be working, I already explored that option. If you put Activello’s demo (https://colorlib.com/activello/) on Google PageSpeed Insights (PageSpeed Insights) it claims the same fails, on the main site is just sending the full picture and rezising it through CSS later in the browser, consuming bandwidth.
Ok i understood it now what you meant and this is happening because the featured images in this theme have different sizes like on the full width page without sidebar it will be displayed very much large and on the page having sidebar it will be displayed smaller and on the home page after first two posts it is displayed even much smaller so in this theme the featured image size is set large according to full width page and then resized using CSS.
To avoid this we have to display different featured image having different size based on what is the layout of page and in what location it is displaying in the front page of the site.
To achieve this you have to develop custom code.
Developing custom code for custom functionality is beyond the scope of support that we provide here.
If you are not a developer then you can consider hiring a developer to develop it for you. You can hire a developer from any freelance site. Colorlib recommends the developer https://www.upwork.com/freelancers/~011652ffec8865c6d5
We will do consider this as a feature request for future development of theme.