Autoptimize minifies JS and CSS and then eliminates render-blocking JavaScript and CSS in above-the-fold content.The best Autoptimize settings help to speed up your WordPress website.This Autoptimize plugin works perfectly with the combination of WP Super cache.If you use this plugin along with W3 total cache plugin, then just disable CSS & JS minification.
Install and activate Autoptimize plugin, then navigate to Settings => Autoptimize.By default you will get HTML, CSS, JavaScript and CDN options.Simply enable the relevant options as shown in image and click on save changes.
HTML Options:
Otimize HTML Code? : Enable
Enable : Keep HTML comments? Enable this if you want HTML comments to remain in the page, needed for e.g. AdSense to function properly.
JavaScript Options
Optimize JavaScript Code? :Enable
CSS Options
Optimize CSS Code? :Enable
Disable : Generate data: URIs for images? Enable this to include small background-images in the CSS itself instead of as separate downloads.
Still some issues are there in Autoptimize 1.9 , in the upcoming versions you will see the complete control on inline and defer CSS. You need to enter optimized CSS code manually in advanced options of Autoptimize settings to completely eliminates render-blocking CSS in above-the-fold content.
Async JS and CSS plugin is the best alternative to this Auto optimize WordPress plugin. It was not updated for the past couple of years, even though, it's working perfectly.