({ addUtilities }: any) => { addUtilities({ ".container-custom": { "@apply mx-auto w-[90%] max-w-[1800px] md:w-[96%] lg:w-[90%]": {}, }, ".container-custom2": { "@apply max-w-[1800px] mx-auto": {}, }, ".container-custom3": { "@apply max-w-[1000px] mx-auto": {}, }, ".mt-section": { "@apply mt-16 md:mt-24": {}, }, ".py-section": { "@apply py-16 md:py-24": {}, }, ".mb-section": { "@apply mb-10 md:mb-16": {}, }, ".mt-element": { "@apply mt-3 md:mt-4": {}, }, ".only-mobile": { "@apply lg:hidden": {}, }, ".non-mobile": { "@apply hidden lg:flex": {}, }, ".flex-gap": { "@apply gap-y-14 gap-x-12": {}, }, ".flex-center": { "@apply flex justify-center items-center": {}, }, ".paragraph": { "@apply text-base font-[400] text-[#BABABA]": {}, }, ".h1": { "@apply scroll-m-20 text-4xl font-extrabold tracking-tight lg:text-5xl": {}, }, }); },@layer utilities { .my-custom-class { background-color: #f5f5f5; border-radius: 4px; padding: 8px; } } In this example, we're using the @layer directive to add a new utility class to the utilities layer. The my-custom-class class has a gray background, rounded corners, and a bit of padding. Once you've defined your custom class, you can use it in your HTML like any other Tailwind CSS utility class: <div class="my-custom-class">This div has a custom class!</div>/** @type {import('tailwindcss').Config} */ module.exports = { theme: { screens: { sm: '480px', md: '768px', lg: '976px', xl: '1440px', }, colors: { 'blue': '#1fb6ff', 'pink': '#ff49db', 'orange': '#ff7849', 'green': '#13ce66', 'gray-dark': '#273444', 'gray': '#8492a6', 'gray-light': '#d3dce6', }, fontFamily: { sans: ['Graphik', 'sans-serif'], serif: ['Merriweather', 'serif'], }, extend: { spacing: { '128': '32rem', '144': '36rem', }, borderRadius: { '4xl': '2rem', } } } }To have tailwindCSS classes to work from JS file- You need to **define the path of js file** in the content portion of **tailwind.config.js** file. Example: <br> content: ["./*.{html,js}", "./src/**/*.{html,js}"] Using this, your tailwind compiler will know that you are trying to add a css class from your JS file and that class will appear in the output css file. Content Configuration is mentioned and explained in details - [**Here [Official Documentation]**][1] [1]: https://tailwindcss.com/docs/content-configuration#pattern-recommendations