tailwindcss/packages/@tailwindcss-postcss
Lazizbek Ergashev 9b0e8af258
Ensure @tailwindcss/postcss rebuilds when the input CSS changes but its mtime is unchanged (#20310)
## Summary

`@tailwindcss/postcss` chooses between an incremental and a full rebuild
by comparing the mtimes of the entry file and its resolved
`@import`/`@config`/`@plugin` graph. It never looks at the input CSS
itself, so when that CSS is produced by an upstream tool (e.g. Sass) and
passed to the plugin via `process()`, it can change while the `from`
file's mtime stays the same. The plugin then re-emits its previously
cached output and silently drops the change.

This stores the input CSS per cache entry and takes the existing full
rebuild path when it differs from the previous compile, mirroring the
fix the CLI watcher already has for changed input files.

Fixes #20307

## Test plan

- Added a regression test in
`packages/@tailwindcss-postcss/src/index.test.ts` that compiles two
different inputs for the same on-disk `from` file (unchanged mtime) and
asserts the second compile reflects the new CSS.
- Confirmed it fails on `main` (the second compile returns the stale
first output) and passes with the fix.
- Ran the `@tailwindcss/postcss` package tests (all green) and checked
formatting with Prettier.

---------

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>
2026-07-06 11:32:20 +00:00
..
src Ensure @tailwindcss/postcss rebuilds when the input CSS changes but its mtime is unchanged (#20310) 2026-07-06 11:32:20 +00:00
package.json 4.3.2 (#20281) 2026-06-29 10:10:00 -04:00
README.md Fix issue around resolving paths in @tailwindcss/vite (#19947) 2026-04-21 14:11:46 +02:00
tsconfig.json Bump dependencies (#19957) 2026-04-24 21:21:12 +02:00
tsup.config.ts Resolve @import in core (#14446) 2024-09-23 17:05:55 +02:00

Tailwind CSS

A utility-first CSS framework for rapidly building custom user interfaces.

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Documentation

For full documentation, visit tailwindcss.com.

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Contributing

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@tailwindcss/postcss plugin API

Changing where the plugin searches for source files

You can use the base option (defaults to the current working directory) to change the directory in which the plugin searches for source files:

import tailwindcss from '@tailwindcss/postcss'

export default {
  plugins: [
    tailwindcss({
      base: path.resolve(__dirname, './path'),
    }),
  ],
}

Enabling or disabling Lightning CSS

By default, this plugin detects whether or not the CSS is being built for production by checking the NODE_ENV environment variable. When building for production Lightning CSS will be enabled otherwise it is disabled.

If you want to always enable or disable Lightning CSS the optimize option may be used:

import tailwindcss from '@tailwindcss/postcss'

export default {
  plugins: [
    tailwindcss({
      // Enable or disable Lightning CSS
      optimize: false,
    }),
  ],
}

It's also possible to keep Lightning CSS enabled but disable minification:

import tailwindcss from '@tailwindcss/postcss'

export default {
  plugins: [
    tailwindcss({
      optimize: { minify: false },
    }),
  ],
}

Enabling or disabling url(…) rewriting

Our PostCSS plugin can rewrite url(…)s for you since it also handles @import (no postcss-import is needed). This feature is enabled by default.

In some situations the bundler or framework you're using may provide this feature itself. In this case you can set transformAssetUrls to false to disable this feature:

import tailwindcss from '@tailwindcss/postcss'

export default {
  plugins: [
    tailwindcss({
      // Disable `url(…)` rewriting
      transformAssetUrls: false,

      // Enable `url(…)` rewriting (the default)
      transformAssetUrls: true,
    }),
  ],
}