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Webpack questions/answers you can use to prepare for interviews or test your knowledge.

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Webpack interview questions

View version with answers

Big thanks to TheLarkInn, raybooysen and johannesMatevosyan for contribution.

Table of Contents


  • What is webpack?
  • What is the main difference between webpack and other build tools like gulp or grunt?
  • What is a bundle in webpack?
  • In which environment does webpack work?
  • What is an entry point?
  • What is a dependency graph and how does webpack build it?
  • Which modules design patterns webpack supports out of the box?

Config file

  • What is the format of webpack's config file?
  • Is it possible to have multiple entry points in a single webpack configuration file?
  • Is it possible to define multiple configurations for different environments?
  • How can we generate webpack config file automatically?


  • What is a loader in webpack?
  • Where should loaders be defined?
  • What is the difference between a rule and a loader?
  • Explain this code
      test: /\.scss$/,
      loaders: ['style-loader', 'css-loader?sourceMap', 'sass-loader?sourceMap', 'postcss-loader'],
      exclude: /node_modules/
  • Do loaders work in a synchronous or an asynchronous way?
  • Is it possible to use multiple loaders in the rules single object?
  • Name loaders that you think are very important and helpful.


  • Describe a plugin in webpack.
  • What is the difference between a loader and a plugin?
  • What is the advantage of CompressionPlugin?
  • How can you move some data (e.g css code) from a bundle to a separate file in webpack?
  • Name some plugins you think are important and helpful.
  • Is it possible to write your own plugin?


  • What are some advantages of using webpack-dev-server over simple http server or nginx?
  • On which platform is webpack-dev-server developed?
  • What is Hot-Modules-Replacement?
  • Does it make sense to use Hot-Modules-Replacement in production environment?
  • How to enable source maps in webpack bundles?
  • How to automatically build and update bundles in the browser after a change in source code?
  • What is parallel-webpack and how does it affect webpack's build process?


  • Briefly describe long-term caching and how to achieve it using webpack?

  • What is difference between

       output: {
        filename: "[name].[hash].js"


        output: {
         filename: "[name].[chunkhash].js"
  • Describe the CommonsChunkPlugin.

  • Explain this code

   new webpack.optimize.CommonsChunkPlugin({
     name: 'common',
     filename: 'common.js',
     chunks: ['home', 'dashboard']
  • Which built-in plugin should be used for code minification?
  • Explain this code
   new webpack.ContextReplacementPlugin(
  • How to remove unused selectors from css using webpack?
  • How to achieve lazy loading in webpack?
  • Why is OccurenceOrderPlugin part of webpack optimization? What it has to do with module ids and topological sorting?
  • What analysis tools do you use for webpack bundle's inspection?


  • Describe the LoaderOptionsPlugin.
  • Do you need to include OccurenceOrderPlugin in the plugins section when use webpack 2/3?
  • Which version(s) of webpack support es6 modules out the box?
  • Which version(s) of webpack support json-loader out the box?
  • Which version(s) of webpack support code splitting?

Advanced questions

  • Describe the webpack runtime and manifest.
  • Is it possible to use other languages (except javascript) for the webpack config file?
  • Is it possible to have different configuration files for different environments?
  • Describe the tree shaking mechanism.
  • What is the difference between tree shaking and dead code elimination.
  • Describe scope hoisting in webpack 3.
  • What is Tapable and how does it relate to webpack plugins?

Internal API Questions (very advanced)

  • What is the difference between Compiler and Watching classes?
  • Describe the purpose of Compiler
  • Describe the purpose of Compililation
  • Describe DependenciesBlock class. Why is it so important?
  • Describe the relationship between the Parser, Dependency, Dependency Factory, and Dependency Templates


Webpack questions/answers you can use to prepare for interviews or test your knowledge.







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