I recently encountered this error in my Terminal when working with TailwindCSS and attempting to build my final CSS file.
Invalid PostCSS Plugin found at: plugins
The plugin error was referring to AutoPrefixer. When I commented out Autoprefixer as a plugin in my postcss.config.js file and ran my build script again (
postcss tailwind.css -o style.css), the error was gone and the CSS file was built – but without AutoPrefixer.
Downgrading Autoprefixer to version 9 did the trick.
So, in my package.json file – I downgraded autoprefixer to version 9.x.
Then, I just ran
npm i to downgrade the package.
You need to downgrade Autoprefixer to 9.x, since postcss-cli do not support PostCSS 8 pluginshttps://t.co/JMgJPYDKlA— Sitnik the Developer (@sitnikcode) September 17, 2020
Disabling Autoprefixer could lead to bugs in old Safari
PostCSS was updated to version 8, however, PostCSS CLI has not yet been updated to handle PostCSS plugins which use the new PostCSS 8+ API. Autoprefixer uses the new PostCSS 8 API since version 10.
This is documented under known issues in the PostCSS GitHub page.
Once PostCSS CLI is updated to handle plugins that use the new PostCSS 8+ API, this will likely not be an issue. But until then, you may need to downgrade some PostCSS plugins to avoid errors.