moduleresolver

Moduleresolver is a software component responsible for translating module identifiers into concrete module resources in modular systems. It is used by runtimes, bundlers, and plugin architectures to locate, load, and optionally transform modules based on a set of resolution rules.

A moduleresolver takes inputs such as a module specifier (for example, "library/foo" or "./local.js"), a referring module (the module that performs the import), and a resolution context (environment, available module paths, package manifests, or import maps). It performs normalization, extension inference, and path resolution, and returns a resource locator such as a URL or file path. In many environments the resolver also handles version selection, package.json fields (main, exports), and conditional exports, as well as aliasing and overrides.

Resolvers can be implemented as synchronous or asynchronous components and are often composable into a chain or graph. They usually incorporate caching to avoid repeating I/O, detect circular dependencies, and support hot-reload or revalidation strategies. They may support multiple module systems (CommonJS, ESM, AMD) or distinguish between source files and pre-bundled artifacts, depending on the toolchain.

In practice, moduleresolvers appear in bundlers like webpack, rollup, and esbuild; in runtime module loaders of Node.js and modern browsers; and in package managers that resolve dependencies for packaging. They interact with loaders, import maps, and manifest data to determine the final loaded module.

Related concepts include module loaders, dependency graphs, and import maps.