How to check if Tailwind actually purges css?

I have a gatsby site, and I want to bring the css bundle size down. I was using the popular plugin gatsby-plugin-purgecss, but it breaks my site even with configurations, and recently tailwind seemed to have added direct support for purgecss: https://tailwindcss.com/docs/controlling-file-size

However, when using the new method with purging directly from tailwind, I can't tell if the css is being purged or not.

Here is my tailwind.config.js

module.exports = {
  purge: [
    './src/**/*.html',
    './src/**/*.jsx',
  ],
  future: {
    removeDeprecatedGapUtilities: true,
    purgeLayersByDefault: true,
  },
  theme: {
    extend: {
      backgroundColor: {
        primary: 'var(--color-bg-primary)',
      },
    },
  },
  variants: {},
  plugins: [],
};

When I run gatsby build && gatsby serve, nothing in the terminal suggests that the css bundle is being reduced. How can I check?