"Selector can't has classes from different scopes" — how to fix this csso error

Wed, 30 Sep 2026 00:00:00 +0000

Your webpack build fails during CSS minification with:

Selector can't has classes from different scopes

What it actually means

This error comes from csso, the CSS minifier. It only happens when your build passes usage data with scopes to csso — typically through css-minimizer-webpack-plugin (with the csso minifier) or csso-webpack-plugin.

Scopes are csso’s way of understanding CSS Modules-style isolation: you tell csso which class names belong to the same “scope” (i.e. they never appear on the same markup), and csso can then merge rulesets more aggressively. Per the csso docs, the exception throws in exactly two cases:

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"Selector can't has classes from different scopes" — how to fix this csso error

What it actually means