Unknown at rule @theme in style.css

[antonijo01]

What version of Tailwind CSS are you using?

v4-alpha

What build tool (or framework if it abstracts the build tool) are you using?

VSCode

What version of Node.js are you using?

Node v21.0.0.

What browser are you using?

Chrome

What operating system are you using?

Windows

Reproduction URL

localhost

Describe your issue

After installing via CLI, I tried to add @theme to style.css and got an error.

[wongjn]

It's a warning from VSCode's in-built CSS parser/validator in that it does not recognize the @theme at rule, since it is indeed not a CSS feature but specific to Tailwind. Nothing to worry about and it should not directly impact using Tailwind.

[depsimon]

You can fix this by changing the Language Mode to Tailwind CSS if you use the Tailwind CSS IntelliSense VS Code extension.

[candidia]

When you do that, you can no longer format the file: "There is no formatter for 'tailwindcss' files installed."

[LestevMisha]

Hey, I was dealing with the same issue, there was no extensions for it out there. So I made one for myself, if you still need it, here https://marketplace.visualstudio.com/items?itemName=MishaLestev.tailwind-css-language-mode-formatter (Tailwind CSS Language Mode Formatter). On Github

[Lord-Gown]

Just install the postcss language support extension for vscode since tailwind uses that also

[sydneyvaughn75-ops]

Tested and it good thank you

…

On Tue, Mar 17, 2026, 5:08 PM JoshuaSineta ***@***.***> wrote: Just install the postcss language support extension for vscode since tailwind uses that also — Reply to this email directly, view it on GitHub <#13205 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/B7HZNK2M4RZ7OMAVQBQOVYT4RHEEDAVCNFSM6AAAAACWVR5TF2VHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMMJYGQ2DCNI> . You are receiving this because you are subscribed to this thread.Message ID: <tailwindlabs/tailwindcss/repo-discussions/13205/comments/16184415@ github.com>