Similar to _.gitignore_ the .dockerignore is a file in which you can specify files/directories you want to exclude from your docker image at build time.

A good use-case example, if you're developing with _nodeJS_, is to include the _nodes_modules_ directory in .dockerignore, since it is relatively large and needs not to be copied every time you build the image as you'll run the `npm install` command in your _dockerfile_ anyway.

#.dockerignore
1 node_modules
2 .dockerignore
3 Dockerfile