🎉 Thanks for being brave and donating your valuable time to testing unfinished beta software 🎉

webpack 5 is in beta phase now. This means major changes and features are done. Major breaking changes have been added. Basic backward-compatibility has been added.

We want to use the beta phase to do the following:

• Let a boarder range of users test the beta version.
• Find bugs in new features.
• Find regressions in old features.
• Find places where a compat-layer can be added to avoid breaking changes.
• Improve the migration guide and changelog.

We want to reach these goals after the beta phase:

• Old features are very stable
• New features are a bit stable
• Backward-compatibility layer allows most existing plugins/loader to work unmodified (potentially with deprecation warnings)
• There clear way how to migrate from webpack 4 to 5
• There are experimental webpack 5 branches for higher-level tools (like angular-cli, vue-cli, create-react-app, ...) (at least 2)

To help with testing you can do the following:

• Always test with the latest webpack beta version, as problems might already be fixed there
• When using webpack directly:
  • Follow the migration guide
  • Report or add missing steps in the migration guide
  • Report problems during the migration
  • Report problems with the build after the migration
• When using a higher-level tool:
  • Check if there is a branch/Pull Request for webpack 5
  • Follow guide there
  • Report problems in the Pull Request
• Make sure to also report (positive) experience
  • Performance comparison
  • Size comparison
  • DX comparison
• Try new features
  • Enable persistent caching -> guide
  • Enable Top Level Await
  • Enable the new asset module type
  • Enable Long Term Caching
  • Try to break filesystem watching
• Trace back deprecation warnings with node --trace-deprecation
  • Help upgrading plugins/loaders
• Make sure to follow beta releases
  • Retest newer version to avoid regressions in beta versions
• Consider sponsoring webpack when this version
  • increases your productivity with better build performance
  • increases your productivity with better developer experience
  • increases your consumer happiness with better application performance
  • make you happy in some other way...

Known problems:

• eval() causes problems with the optimization.innerGraph (production).
• libraryTarget: "module" is not implemented yet
• devtools don't support persistent caching yet
• Persistent Cache file include absolute paths are are not portable yet
• import.meta is still missing
• prefetching doesn't work for WASM yet
• CLI arguments doesn't contribute to cache version
• stack trace is incorrectly displayed in stats
• Build Time is a bit higher for non-cached builds. Possible reasons:
  • tracking extra information in the resolver for safe caching
• mini-css-extract-plugin is not able to persistent cache yet
• Crashes when using lintDirtyModulesOnly and webpack 5.beta0 webpack-contrib/stylelint-webpack-plugin#187
• svg-sprite-loader doesn't work
• There is no warning for Buffer or process yet.

Planned breaking changes:

• devtool options will be more restrictive
• Internal HMR API for plugins will probably change
• Disable some webpack-only syntax by default: require.ensure, require.include
• terser-webpack-plugin will be upgraded
• cache.store != "pack" will be removed