Find answers to common questions about our service
We use a cluster of headless Chromium browsers controlled by Puppeteer. When you submit a URL, we render the page, execute JavaScript, and capture the computed styles for all visible elements.
Yes. Because we use a real browser engine, we execute your JavaScript before extracting CSS. This means we can capture styles for elements that are dynamically added to the DOM.
We recommend preloading critical fonts. Our tool focuses on the CSS rules. You should ensure your `@font-face` definitions are included in the critical CSS or loaded efficiently to avoid FOUT/FOIT.
Yes, we preserve CSS variables that are used in the critical path. This ensures your theming and dynamic colors remain consistent.
We extract all media queries that apply to the critical viewport. This ensures your site remains responsive even with just the critical CSS loaded.
Our API allows you to specify custom viewport dimensions if you have specific requirements. By default, we test standard mobile and desktop resolutions.
Cookie banners often appear above the fold. Our generator usually captures their styles so they render correctly. If they are blocking the view, you might want to exclude them via custom CSS.
Shadow DOM styles are encapsulated. We do our best to extract styles, but deep Shadow DOM implementations might require manual tuning depending on your architecture.
We use a standard Chrome user agent. If your firewall blocks bots, you may need to whitelist our service IP or User Agent string.
By inlining the Critical CSS in the `<head>`, the browser can paint the content immediately. This eliminates FOUC for the critical area.
Our generator analyzes your URL using a headless browser to determine exactly which styles are applied to the visible elements within the viewport. It then extracts these styles and generates a minified CSS block for you to use.
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