This is my project configuration:
"webpack": "^4.16.5",
"webpack-cli": "^3.1.0",
"webpack-dev-server": "^3.1.5"
When I run npx webpack --config webpack.config.js everything is running as expected - all of the assets are compiled and assets folder is created.
When I run webpack-dev-server command only a server is started, the assets are compiled, but the assets folder is not created.
The assets folder is not created because webpack-dev-server or webpack-dev-middleware creates all your bundler in memory. This means that the browser is going to access the content served from the memory by webpack-dev-server.
When you directly run webpack, that creates actual files. Nothing is wrong here.