First Contentful Paint (FCP)

Critical CSS For WP is available on the repository ahmedkaludi/critical-css-for-wp. This is the first free plugin specifically created to extract Critical CSS. However, the main library responsible for this function is JanDC/critical-css, a PHP library dedicated to generating Critical CSS. This library exclusively utilizes PHP without Node.js to extract Critical CSS for each page.

Generate Critical CSS? for free? Swift Performance Lite Swift Performance Review And Optimal Settings + Cloudflare 2020

Also check: Debloat – Remove Unused CSS, Optimize JS

Ways to generate Critical CSS

GoogleChromeLabs/critters: 🦔 A Webpack plugin to inline your critical CSS and lazy-load the rest. pocketjoso/penthouse: Generate critical css for your web pages addyosmani/critical: Extract & Inline Critical-path CSS in HTML pages Optimize CSS delivery for faster page rendering

Website Speed Test | Choose your test location How to Generate Critical Path CSS in WordPress

Removing unused CSS with Purgecss/UnCSS - sage - Roots Discourse

Remove unused CSS with PurgeCSS

Some plugins:

Core Web Vitals & PageSpeed Booster

Advanced Critical CSS Generator and plugin WP Core Web vitals