Webpack 5.111: ESM output stable, output.copy, CSS targets (14 Sep 2026)

On 14 September 2026, the webpack project published Webpack 5.111. The release makes ES module output stable (you can drop experiments.outputModule and keep output.module), adds built-in output.copy for static/public files, expands browserslist-aware CSS lowering and color fallbacks, renames several performance hint options, ships a smaller chunk-loading runtime, drops acorn and neo-async as dependencies, and fixes hot updates and caching. ShopperCove did not upgrade a production webpack pipeline for this note and did not run build benchmarks. On 5 October 2026, npm dist-tag latest resolved to webpack@5.111.1 (published 18 Sep 2026); the feature blog and GitHub tag cover the 5.111.0 line that shipped 14 Sep 2026. This is a docs-based upgrade checklist—not performance advice and not a security advisory (no CVEs are claimed here).

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ESM output without an experiment

If you ship an app or library as ES modules, remove experiments.outputModule and keep output.module: true. ESM output is stable; module / modern-module library types and externalsType: "module" no longer need the experiment flag.

Upgrade gotcha: if you only had experiments.outputModule: true, add output.module: true. Webpack ignores the old flag alone, so keeping it without output.module will not enable ESM output.

A module or modern-module library type now turns output.module on by itself. experiments.futureDefaults now includes output.module where the target can read modules (classic script output still wins for targets that cannot, for script-style library types such as var/umd, or when you set output.module yourself).

Async startup: if an entry uses top-level await, importers wait until that setup finishes (and receive errors on failure) when the target supports TLA; override with output.environment.topLevelAwait if needed.

ES module libraries and externals also improve: live bindings on re-exports from externals, respect for your externals mapping on star re-exports, import attributes kept, cycle stack overflows fixed, and a build error when export * targets an external declared as an array (specifier + property path).

File URLs and copying static files

ESM webpack configs can pass file: URL strings to path options such as context and output.path (and to rule test/include) without wrapping fileURLToPath()—pass the URL .href string, not a URL object.

output.copy copies folders that nothing imports (for example robots.txt, public images, licenses) into the output directory as part of the build:

export default {
  output: {
    copy: "public",
  },
};

Patterns support from/to, contenthash filenames, filters, transforms, and permission/timestamp preservation. Watch mode recopies edits; files appear in stats and survive output.clean. Overwriting a generated asset is an error; empty patterns warn. For more control, use built-in CopyPlugin.

CSS for browser targets + HTML

With a browserslist target, the built-in CSS minimizer’s lowerUnsupported and colorFallbacks (on by default) cover more syntax—including inset, media ranges, and CSS nesting—and improve math/color simplification. Tune via optimization.minimize.css. Optional knobs include unusedSymbols, pseudoClasses, resolveCustomAtRules, rewriteDirSelector, and mergeDistantRules (off by default).

HTML native support: trim whitespace around URL attributes; optional mergeScripts and broader collapseBooleanAttributes; attribute minification no longer depends on quote spelling; plugins can reuse webpack.css.syntax.cssMinify / webpack.html.syntax.htmlMinify; NormalModule processResult can be async (for example image format conversion with module.buildInfo.assetResource).

Performance hints rename (breaking config names)

If you enabled checks in 5.110, update renamed options or webpack reports a configuration error:

New/clarified checks also include unusedAssets and analyzableBailouts. Use performance.hints: "stats" to explore findings without warning-level build noise. Note: hints: false silences bundle checks but enabled configuration checks still warn—turn those options off individually.

Smaller output, own parser, cache, namespaces

• Chunk-loading runtime shrinks (__webpack_require__.e / priority queue emission).
• With ESM output, chunk imports move into the chunk loader; rebuilds invalidate less when lazy routes change.
• Idle/watch memory lower (blog cites ~6.3 MB off an 85.6 MB idle heap on a 1700-module project).
• Webpack parses JavaScript with its own parser; acorn and neo-async are no longer dependencies.
• Filesystem cache buildDependencies may mark entries optional: true so a missing shared config file does not block saving the cache.
• Optional module.parser.javascript.specNamespaceObject for more native-like import * namespace objects (Proxy cost / less merging)—most apps leave this off.

Also: resolve.fileSystem is honored; module.exprContextCritical deprecation points at module.parser.javascript.exprContextCritical; DefinePlugin undefined property reads throw like native.

Bug fixes (blog summary)

More reliable CSS hot updates and cache invalidation; async init / optimized JS / CSS in server and loader workflows; clearer errors for missing assets and runtime codegen; scope-hoisting and HTML </ escaping fixes; DelegatedModule / cached resolveOptions / inlined-value consumer regeneration. Prefer the 5.111.0 release notes for the full contributor list.

Hands-on upgrade checklist

1. Inventory: npm ls webpack / lockfile. Note whether you are on 5.110.x or earlier.
2. Pin in staging: install webpack@5.111.1 (or at least 5.111.0). Confirm with npm view webpack version (expect 5.111.1 as latest as of sources read 5 Oct 2026).
3. ESM migration: replace lone experiments.outputModule with output.module: true; verify library/externalsType module setups.
4. Static assets: try output.copy for public/ instead of a separate copy step; confirm watch + output.clean behavior.
5. Performance config: rename options per the table above before CI fails on unknown keys.
6. CSS/HTML: if you rely on browserslist CSS minify, spot-check inset/nesting/color output; re-test HMR for CSS.
7. Do not invent security urgency: the official blog frames features, size/memory, and bugfixes—ShopperCove is not attaching CVE IDs.

ShopperCove did not change production webpack versions for this article. Prefer the official 5.111 blog over third-party roundups.

Bottom line

Webpack 5.111 (blog 14 Sep 2026) stabilizes ESM output, adds output.copy, expands target-aware CSS lowering, renames performance checks, and lightens runtime/deps. Pin webpack@5.111.1 (or 5.111.0+) when ready. No affiliate.

Sources

• 01registry.npmjs.org/webpack/5.111.0
• 02registry.npmjs.org/webpack/5.111.1
• 03npmjs.com/package/webpack

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