developmentDependency

A developmentDependency, in software package management, is a package that is required to develop, build, test, or otherwise prepare a project but is not needed for the software to run in production. These dependencies support tooling, compilers, and test frameworks rather than core application functionality.

Different ecosystems label and handle them in various ways. In npm and Node.js, development dependencies are declared in a project’s package.json under the devDependencies field. When installing for production, tools often omit these packages (for example, npm install --production or npm ci with production settings). Other ecosystems have analogous concepts, such as Rust’s [dev-dependencies] in Cargo, or Python’s test or extra requirements used during development rather than at runtime.

Common examples of developmentDependencies include testing frameworks (for example, Jest or Mocha), build and transpilation tools (Webpack, Babel), type checkers (TypeScript), linters (ESLint), code formatters, and scaffolding utilities. These tools facilitate development workflows but are not typically required by end users of the software.

Best practices emphasize separating development dependencies from runtime dependencies to minimize production footprint and security risk. Projects should ensure that production builds do not rely on dev tools, that CI pipelines install with access to development dependencies for testing, and that version ranges are chosen to balance stability with up-to-date tooling. Misconfigurations can lead to bloated production bundles or missing tooling at build time.