How to remove Tailwind from a Phoenix project

There's a chance you have an existing Phoenix project that has been created with the default option of having TailwindCSS integrated, but you would like to go vanilla CSS.

Steps

1. Remove :tailwind from mix.exs

2. Remove related commands from aliases in mix.exs (make sure to preserve any esbuild builds if you are using that).

3. Remove @import "tailwindcss/... from app.css

4. Open js/app.js and add import "../css/app.css" to it.

5. Delete file /assets/tailwind.config.js

6. Remove block starting with config :tailwind from config.exs

7. Remove tailwind: {Tailwind, :install_and_run, [:default, ~w(--watch)]} from watchers inside dev.exs

8. Run mix deps.clean --unlock --unused

You may have to fix layout related issues, how you render flash messages, and adjust core_components.exs.

Original solution found in Elixir Forums.