Node.js

Node.js is a JavaScript runtime for computers and servers. In React Native it is the engine behind your tooling: Metro, Expo CLI, the React Native CLI, package managers, Jest and the build scripts that Xcode and Gradle call during a native build all run on Node.

Your app does not. On the device your code runs on Hermes, a different JavaScript runtime with no Node APIs. This is the most common misconception for developers arriving from backend or web tooling:

• fs, path and child_process do not exist in the app, and process.env only holds values inlined at build time.
• npm packages that depend on Node built-ins, such as many crypto or file libraries, will fail to bundle or crash when called. Look for React Native-specific alternatives.
• Buffer is not a global by default.

React Native and Expo each declare a minimum Node version in their packages, and it rises over time. Use an active LTS release and pin it per project so everyone on the team, and CI, gets the same version. Version managers such as nvm, fnm or Volta read a file at the repository root:

echo "22" > .nvmrc
nvm use

The classic setup gotcha: the app builds from the terminal but fails in Xcode with "node: command not found" or the wrong version. Xcode does not load your shell profile, so it cannot see a Node installed through a version manager. React Native projects solve this with ios/.xcode.env, and you can override it locally in ios/.xcode.env.local:

export NODE_BINARY=$(command -v node)

Upgrading Node also changes the native modules your tooling depends on, so reinstall node_modules after switching major versions.