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addyosmani avatar

addyosmani/critical

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Critical

Critical is a tool for extracting and inlining the minimum CSS required to render above-the-fold content. It identifies the styles necessary for the initial visible portion of a page to reduce render-blocking requests and improve page load speed.

The project generates resolution-specific stylesheets to optimize the initial paint across different device dimensions. It includes a utility to rebase asset URLs within extracted styles, ensuring that images and fonts load correctly when stylesheets are moved to different directories or content delivery networks.

The tool provides a command-line interface for integrating the extraction process into automated build pipelines. It supports excluding specific selectors from being inlined to defer non-essential assets and uses headless browser analysis to match CSS rules against the visible viewport.

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Features

  • Above-the-Fold Optimization - Identifies and inlines the minimum styles needed to render the initial visible portion of a page.
  • Multi-Resolution Generation - Generates tailored stylesheets for different screen dimensions to ensure optimal above-the-fold rendering across various devices.
  • AST Transformation Tools - Provides utilities for parsing and transforming stylesheets via abstract syntax trees to prune unused rules.
  • Resolution-Specific Generation - Creates tailored critical CSS for different screen resolutions to ensure optimal rendering across device dimensions.
  • Performance Tuning - Optimizes the responsiveness and speed of the frontend by reducing render-blocking CSS requests.
  • Critical Style Extraction - Identifies and extracts the minimum styles required to render the above-the-fold content for specific resolutions.
  • CSS Inlining - Injects extracted critical styles directly into the HTML document to eliminate render-blocking requests.
  • Headless Browsers - Uses headless browser engines to render pages and determine which CSS rules are active in the viewport.
  • DOM-Based Style Mapping - Traverses the rendered page document to map active style declarations back to their source definitions.
  • Static Style Generators - Functions as a build-time tool that compiles critical styles into static CSS to optimize initial paint.
  • Viewport-Based Style Filtering - Identifies critical styles by matching CSS selectors against DOM elements visible at specific screen resolutions.
  • CSS Build Tools - Provides a build-time engine that scans source files to generate and optimize critical CSS styles.
  • Scripting and CLI - Ships a command-line interface for integrating the style extraction process into automated build pipelines.
  • Command Line Interfaces - Provides a production-ready command-line application for extracting critical CSS from HTML files.
  • Asset Path Resolvers - Implements systems for mapping and transforming relative asset links within CSS to valid site URLs.
  • Extraction Workflows - Integrates style extraction into build scripts via a CLI to automate critical CSS delivery.
  • CSS Optimization - Extract and inline critical CSS for faster rendering.
  • Web Performance Utilities - Extracts and inlines critical-path CSS.
10,183 stars·380 forks·JavaScript·apache-2.0·24 views

Star history

Star history chart for addyosmani/criticalStar history chart for addyosmani/critical

How this analysis was created: This summary and feature list are AI-generated from collected project material and can contain mistakes. Stars, license and language are imported from GitHub. Inclusion does not mean that we have tested or audited this project. Check the source documentation for any feature you depend on. Learn more on our About page.

Projects sharing features with Critical

These projects share indexed features with Critical. Shared tags can include platform or build tooling; verify the primary use case before treating a result as a replacement.
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    stereobooster/react-snap

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    react-snap is a static site generator and single-page application prerenderer. It converts dynamic client-side components into static HTML files using a headless browser to improve search engine optimization and initial load speeds. The project features a headless browser crawler that automatically discovers application routes by following internal links. It includes a hydration optimizer that captures application state and caches network responses during the rendering process, embedding them directly into the HTML to synchronize the client-side application without re-fetching data. The tool

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    tijsverkoyen/CssToInlineStyles

    5,831View on GitHub↗

    CssToInlineStyles is a CSS inliner for HTML emails that converts stylesheets into inline style attributes on HTML elements. It functions as a style resolver and transformation engine, mapping CSS selectors to HTML tags to ensure consistent visual rendering across diverse email clients and providers. The tool calculates final computed styles by applying specificity and inheritance rules before injecting the resolved properties directly into the style attributes of the corresponding HTML elements. It utilizes DOM-based style calculation and selector mapping to determine which declarations apply

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  • vanilla-extract-css/vanilla-extractvanilla-extract-css avatar

    vanilla-extract-css/vanilla-extract

    10,387View on GitHub↗

    vanilla-extract is a type-safe CSS-in-JS library and zero-runtime CSS framework. It uses TypeScript to define styles and design tokens, compiling these definitions into static CSS files during the build process to eliminate styling overhead in the browser. The system acts as a scoped CSS generator, producing unique class names and local variables to prevent global style leakage and naming collisions. It provides a type-safe styling tool that validates CSS property values and ensures design tokens adhere to defined themes during development. The framework covers comprehensive styling utilitie

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  • postcss/postcsspostcss avatar

    postcss/postcss

    28,968View on GitHub↗

    PostCSS is a CSS post-processor and abstract syntax tree transformation tool that parses stylesheets into a structured tree for programmatic analysis and modification. It functions as a plugin-driven pipeline where JavaScript plugins can modify, insert, or delete nodes to transform styles. The project provides a framework for building a custom plugin ecosystem to extend the CSS language with non-standard features such as loops, conditionals, and shorthand properties. It supports multi-syntax parsing through pluggable parsers and stringifiers, allowing it to process various style formats and c

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Compare all 30 related projects→

Frequently asked questions

What does addyosmani/critical do?

Critical is a tool for extracting and inlining the minimum CSS required to render above-the-fold content. It identifies the styles necessary for the initial visible portion of a page to reduce render-blocking requests and improve page load speed.

What are the main features of addyosmani/critical?

The main features of addyosmani/critical are: Above-the-Fold Optimization, Multi-Resolution Generation, AST Transformation Tools, Resolution-Specific Generation, Performance Tuning, Critical Style Extraction, CSS Inlining, Headless Browsers.

Which projects share features with addyosmani/critical?

Projects with overlapping indexed features include: stereobooster/react-snap — react-snap is a static site generator and single-page application prerenderer. It converts dynamic client-side… vanilla-extract-css/vanilla-extract — vanilla-extract is a type-safe CSS-in-JS library and zero-runtime CSS framework. It uses TypeScript to define styles… tijsverkoyen/csstoinlinestyles — CssToInlineStyles is a CSS inliner for HTML emails that converts stylesheets into inline style attributes on HTML… uncss/uncss — Uncss is a build pipeline CSS optimizer and optimization tool designed to remove unused styles from stylesheets. It… postcss/postcss — PostCSS is a CSS post-processor and abstract syntax tree transformation tool that parses stylesheets into a structured… cssnano/cssnano — cssnano is a CSS compression tool and minifier that reduces the file size and gzip footprint of stylesheets. It…