npm 'WARN EBADENGINE Unsupported engine { package: ..., required: { node: ">=20" }, current: { node: "v18..." } }' (or 'error notsup' / engine-strict). What does it mean and how do I resolve it?

Cause: packages can declare which Node.js (and npm) versions they support in the "engines" field of package.json. When the installing Node version doesn't match, npm prints EBADENGINE. By default it's only a warning and the install continues, but the package may fail at runtime if it uses newer Node features. If the project or your npm config sets engine-strict=true, npm turns the mismatch into an error and stops (the old 'notsup' error). Yarn and pnpm enforce engines more strictly by default. Fix (best first): 1. Use a Node version the packages support: check the required range in the message, then switch with a version manager (nvm install 20 && nvm use 20, fnm, Volta) or update the Node version in CI (setup-node node-version) and Docker images (FROM node:20...). 2. Pin the project's Node version so everyone uses the same one: an .nvmrc / .node-version file, the "engines" field in your own package.json, and the same version in CI. 3. If you can't upgrade Node yet, install an older version of the dependency that still supports your Node (check its changelog), and pin it. 4. Only as a temporary measure, keep the default non-strict behavior (don't set engine-strict) and test carefully; ignoring the warning doesn't make the package work on an unsupported Node. 5. Upgrading off an end-of-life Node release is worthwhile anyway, since EOL versions get no security fixes. Verify: node --version matches the required range, and npm install completes without EBADENGINE warnings. Sources: https://docs.npmjs.com/cli/v10/configuring-npm/package-json https://docs.npmjs.com/cli/v10/using-npm/config