[v4] Does Tailwind's built-in purge affect source files or just build output?

[alex-x-x-x-x]

I'm using TailwindCSS with React and Vite, and I know that unused utility classes are automatically removed during production builds. I'm curious how this purge (tree-shaking) process works with regard to version control.

Specifically:
Does Tailwind's purge process ever modify source files, or does it only affect the generated output (e.g., dist/) when running npm run build?

In my setup, dist/ is in .gitignore, so I'm assuming purged CSS changes never show up in Git — is that correct?

Just trying to better understand whether purge has any impact on tracked files, and if there are edge cases (like static site setups) where that might differ.

Appreciate any insights, thanks!

[wongjn]

I wouldn't call it purging. That was old phrasing used during Tailwind v2. In this older version, a predefined list of classes where built up in dev. This list would then get trimmed down to only used classes, hence the term "purging". While from v2 JIT onwards, only the used set of classes are built at all. There is no purging in the v2 sense.

Though to answer your question, Tailwind does not modify your source template files at all, during dev or build. It only reads your source template files for Tailwind string class names to build CSS rules from.

[alex-x-x-x-x]

@wongjn Thanks for the clarification! That makes perfect sense now — especially with the shift to JIT in Tailwind v2.1+.

So, just to confirm: the JIT engine only generates the classes you use in your templates, and nothing is ever "purged" or removed from the final CSS because it simply doesn't generate unused classes to begin with.

That clears up my understanding of how Tailwind handles unused classes, thanks for taking time to respond.

[wongjn]

Indeed, the JIT engine only generates the classes you use in your templates, and nothing is ever "purged" or removed from the final CSS because it simply doesn't generate unused classes to begin with.

[alex-x-x-x-x]

@wongjn Perfect, closing this discussion. Short and sweet! Thanks for your time!

[pupunha-dev]

I love Tailwind CSS ❤