The default contents of project.config.js look like this:

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project.config.js

module.exports = {
  gulpthemes: [
    {
      path: '',
      with_styleguide: false
    },
    // uncomment the following to enable it in multiple themes
    // {
    //   path: 'web/themes/custom/compony',
    //   with_styleguide: true
    // },
  ],
  features: {
    autoprefixer: {
      enable: true,
      options: {
        browsers: ['last 2 versions', 'ie 9', '> 0.2%'],
        cascade: false
      },
    },
    browserify: {
      enable: true,
      debug_mode: false,
      tinyify: {
        enable: true,
        options: {
          flat: false
        }
      }
    },
    clean_css: {
      enable: false,
    },
    css_mapping: {
      enable: false,
    },
    image_optimise: {
      enable: true,
      gifsicle: {
        interlaced: true,
        optimizationLevel: 3
      },
      optipng: {
        optimizationLevel: 5
      },
      jpegtran: {
        progressive: true
      },
      svgo: {
        plugins: [
          {
            removeViewBox: false
          },
          {
            removeDimensions: true
          }
        ]
      }
    },
    sass_includes: {
      bourbon: false,
      bourbonNeat: false,
      breakpoint: false
    },
    uglify: {
      enable: true,
      options: {
        compress: {
          unused: false
        },
        mangle: false,
      }
    },
    // Deprecated
    kss: {
      enable: false,
    },
  },
};

Anything you change in this file will impact the generated files such as CSS and JavaScript of your components, so each change you make in this file, will need to be committed to your repository so that your colleagues also have these same settings.

We have 2 sets of options here: you can choose to link your gulp to 1 or more themes and you can also choose what features you want to enable inside Gulp.