npm / less-loader
less-loader
What changed in less-loader 5 to 13, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-27.
23 breaking1 deprecations10 new APIs and options1 performance4 behavior and defaults2 tooling5 fixes and other
See which of these apply to your code, ranked, in your agent:
npx @unstale/cli initless-loader 136 changes
Breaking changes 2
The option now defaults to true, emitting Less warnings and errors as webpack warnings and errors; set it to false to restore silent logging.
The minimum supported Node.js version is now >= 22.11.0.
New APIs and options 1
The package now ships native ESM as well as CommonJS, with an exports map exposing separate entry points for import and require.
Behavior and default changes 2
Imports from a data: resource are resolved from the loader's context.
Files loaded synchronously by Less, including through data-uri() and custom functions installed via @plugin, are tracked as webpack file dependencies.
Tooling 1
Types have been added for the package.
less-loader 124 changes
Breaking changes 3
Reverts the ESM dynamic import; the notes do not specify further details.
The peer dependency was updated for @rspack/core v2, affecting package compatibility.
The minimum supported Node.js version is now 18.12.0.
Fixes and other changes 1
Fixed compatibility with ECMA modules less version.
less-loader 111 changes
Breaking changes 1
The minimum supported Node.js version is now 14.15.0.
less-loader 102 changes
Breaking changes 1
Removed; use pluginManager.webpackLoaderContext instead.
Performance 1
Fixed memory usage.
less-loader 91 changes
Breaking changes 1
The minimum supported Node.js version is now 12.13.0.
less-loader 84 changes
Breaking changes 2
The loader first resolves @import as relative; if that fails, it resolves it inside node_modules.
The minimum supported webpack version is 5.
Deprecations 1
Using ~ is deprecated and can be removed from imports, though it remains supported for historical reasons.
New APIs and options 1
The loader supports webpack's resolve.byDependency option for configuring resolution by dependency type, including Less-specific mainFiles.
less-loader 77 changes
Breaking changes 4
The appendData option was removed in favor of additionaldata.
The implementation option was removed.
less moved to peerDependencies, so developers must provide the Less implementation as a peer dependency.
The prependData option was removed in favor of additionaldata.
New APIs and options 3
The additionaldata option was added as the replacement for prependData and appendData.
Loader context was added in Less plugins.
A webpackImporter option was added.
less-loader 617 changes
Breaking changes 6
Imports are resolved first with the Less resolver, then with the webpack resolver.
Less version 2 is no longer supported.
Less version 3 is used by default, so developers no longer need to add less to package.json.
Less-specific options move to the lessOptions option.
The minimum supported Node.js version is 10.13.
The minimum supported webpack version is 4.
New APIs and options 5
The appendData option is added.
Packages can now use an index.less file.
The loader now supports the less field in package.json.
The loader now supports the style field in package.json.
The prependData option is added.
Behavior and default changes 2
Import aliases without a tilde are supported.
lessOptions can now be a function.
Tooling 1
webpack 5 is supported.
Fixes and other changes 3
Resolution is fixed for package-file imports using either the package path or a relative package path.
The paths option now works with the webpack resolver.
The loader no longer crashes on remote imports.
less-loader 54 changes
Breaking changes 3
The deprecated compress option was removed.
Support for Node.js versions below 6.9 was dropped.
Support for webpack versions below 4 was dropped.
Fixes and other changes 1
Webpack watching now recovers after broken Less is fixed.