Extract critical css file with record in manifest.json

How I can extract critical css without any html process. I want extract critical file with hash in the name and emit this file as asset to webpack and save it to manifest.json as file Example:

{
  "app.js": "app.0f15f07046d4.js",
  "app.css": "app.395ff6e90875.css",
  "app.js.map": "app.0f15f07046d4.js.map",
  "app.css.map": "app.395ff6e90875.css.map",
  "vendor.js": "vendor.61b7598213e7.js",
  "vendor.js.map": "vendor.61b7598213e7.js.map",
  "critical.css": "critical.g5h32j4k123.css"
}

[romanlex]

@thescientist13 thx for the answer

[thescientist13]

@romanlex To build off @anthonygore , I don’t think it’s in the scope of critical either.

My understanding of how critical works is by actually using a headless browser to render your page and then using the resulting rendering to find the HTML that is “above the fold” and determine the needed CSS from that. So in fact, it requires working off an HTML document.

Per their README

Critical extracts & inlines critical-path (above-the-fold) CSS from HTML

Hope that helps!