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What is the purpose of a .dockerignore file when preparing a Node.js project for cloud deployment?

Beginner

Answer

A .dockerignore file excludes files -- most importantly node_modules, .env files, and local build artifacts -- from being copied into a Docker build context, keeping images smaller and preventing accidentally baking local secrets or a platform-specific node_modules into a production image.
node_modules
npm-debug.log
.env
.git
coverage
Real-world example A team's Docker images failed on a different CPU architecture until adding .dockerignore excluding node_modules, forcing 'npm ci' inside the build to install correctly-architected dependencies.

Common follow-ups: Why can copying a local node_modules folder into a Docker image cause native-module compatibility issues?;What other sensitive files should always be excluded from a build context?

Docker & Containerization for Node.js;Security
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