Why Tailwind CSS doesn't render markdown in React/Next.js

Issue

When I initially made this static blog with Next.js following this tutorial — Static Blog With Next.js and Markdown — below /[slug].js code didn't render markdown properly.

// pages/post/[slug].js
import { marked } from "marked"

export default function PostPage({ ..., content }) {
    return <div className="" dangerouslySetInnerHTML={{ __html: marked(content) }}></div>
}

Upon inspecting elements, I noted that markdown contents are rendered with appropriate HTML tags.

// Inspecting by logging and looking at Elements in Chrome Developer Tools
console.log(marked(content))

This markdown blog post...

<!-- markdown post -->
# title1

will turn into this HTML

<!-- HTML rendered in DOM -->
<h1>title1</h1>

But the respective CSS for the HTML elements were not applied as I was using Tailwind CSS. Turns out Tailwind CSS negates the defaults styles and you need to specify each elements how it should look. <h1>title1</h1> will just be a text with default font size.

Solution

@tailwindcss/typography

Usage

Install plugin package

npm i -D @tailwindcss/typography

Configure

// tailwind.config.js
module.exports = {
  // ...
  plugins: [require("@tailwindcss/typography")],
  //   ...
};

Add prose class

// pages/post/[slug].js
<div className="prose" dangerouslySetInnerHTML={{ __html: marked(content) }}></div>

That's it.

What is prose

prose class adds pre-defined set of styles for all that come inside the scope.

For example, h1 tag in <h1>title1</h1> will have following css applied behind the scene.

.prose :where(h1):not(:where([class~="not-prose"] *)) {
    color: var(--tw-prose-headings);
    font-weight: 800;
    font-size: 2.25em;
    margin-top: 0;
    margin-bottom: 0.8888889em;
    line-height: 1.1111111;
}

You can tweak prose class by adding additional classes related to prose like so

// pages/post/[slug].js
<div className="prose prose-lg" dangerouslySetInnerHTML={{ __html: marked(content) }}></div>

<h1>title1</h1> will then have following styles instead

.prose-lg :where(h1):not(:where([class~="not-prose"] *)) {
    font-size: 2.6666667em;
    margin-top: 0;
    margin-bottom: 0.8333333em;
    line-height: 1;
}

You can customize further by applying more of provided class names or overriding the CSS entirely in your css file like so

// pages/post/[slug].js
<div className="prose prose-lg prose-pre:p-0" dangerouslySetInnerHTML={{ __html: marked(content) }}></div>

/* styles/globals.css */
.prose :not(pre *):where(code):not(:where([class~="not-prose"] *)) {
  margin: 0;
}

.prose :where(a):not(:where([class~="not-prose"] *)) {
  @apply text-blue-700 !important
}