Svelte Render Markdown

21 May 2024

How to master Markdown Rendering in Svelte

Ed Robinson, Lead Software Engineer

Introduction to Rendering Markdown in Svelte

Markdown has become an essential tool for web developers, offering a simple and intuitive way to format and structure content. Its popularity stems from its readability, ease of use, and compatibility with a wide range of platforms and frameworks. In this article, we'll explore the power of rendering Markdown in Svelte, a modern and efficient JavaScript framework for building user interfaces.

For further guides and comparisons of Svelte with other frameworks, click here.

Understanding the Importance of Markdown in Web Development

Markdown's significance in web development cannot be overstated. It allows developers to create rich and well-formatted content without the need for complex HTML or styling. Some key benefits of using Markdown include:

  • Simplicity: Markdown's syntax is straightforward and easy to learn, making it accessible to developers of all skill levels.

  • Readability: Markdown documents are highly readable, even in their raw form, which enhances collaboration and maintainability.

  • Portability: Markdown files can be easily converted to HTML, PDF, and other formats, making them versatile and suitable for various use cases.

  • Consistency: By using Markdown, developers can ensure a consistent formatting style across their projects, improving the overall quality and coherence of their content.

When it comes to building modern web applications, integrating Markdown rendering capabilities becomes crucial. This is where Svelte shines, providing developers with a powerful and efficient way to render Markdown content seamlessly within their applications.

Overview of Svelte's Capabilities for Rendering Markdown

Svelte, as a modern JavaScript framework, offers several advantages for rendering Markdown content:

  • Component-based architecture: Svelte's component-based approach allows developers to create reusable Markdown rendering components that can be easily integrated into any part of their application.

  • Reactivity: Svelte's reactive system enables real-time updates of rendered Markdown content whenever the underlying data changes, providing a smooth and interactive user experience.

  • Performance: Svelte's compile-time approach results in highly optimized JavaScript code, ensuring fast and efficient Markdown rendering, even for large and complex documents.

  • Extensibility: Svelte's flexible architecture allows developers to easily integrate third-party libraries and tools, such as Markdown parsers and syntax highlighters, to enhance the Markdown rendering capabilities.

By leveraging Svelte's strengths, developers can create powerful and interactive Markdown-based applications with ease.

Setting Up a Svelte Project for Markdown Rendering

To get started with rendering Markdown in Svelte, you'll need to set up a Svelte project. Here's a quick overview of the steps involved:

  1. Install Svelte: Use the Svelte CLI or your preferred package manager to create a new Svelte project.

  2. Install Markdown parsing library: Choose a Markdown parsing library that is compatible with Svelte, such as marked or showdown, and install it in your project.

  3. Create a Markdown rendering component: Create a new Svelte component that will handle the Markdown rendering logic. This component will take the Markdown content as input and render it as HTML using the chosen parsing library.

  4. Integrate the component: Use the Markdown rendering component within your Svelte application, passing the Markdown content as a prop or binding it to a data source.

By following these steps, you'll have a solid foundation for rendering Markdown content in your Svelte application.

It's worth noting that using a headless CMS like caisy can greatly simplify the process of managing and delivering Markdown content to your Svelte application. With a headless CMS, you can store your Markdown files centrally, leverage powerful content management features, and easily integrate with your Svelte frontend using APIs. This approach allows developers to focus on building the user interface while benefiting from a robust and flexible content management system. Learn what makes caisy the perfect Headless CMS for developers.

In the following sections, we'll dive deeper into the specifics of parsing Markdown, building a Markdown editor, implementing syntax highlighting, and creating a Markdown-powered blog using Svelte. So, let's embark on this exciting journey of mastering Markdown rendering in Svelte!

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Parsing Markdown Content in Svelte

When it comes to rendering Markdown content in a Svelte application, developers have several options to choose from. In this section, we'll explore the various approaches to parsing Markdown and integrating it seamlessly into your Svelte components.

Exploring Markdown Parsing Libraries Compatible with Svelte

One of the challenges developers face when working with Markdown in Svelte is finding a compatible parsing library. Many popular Markdown libraries, such as markdown-it and marked, expect to find Node.js or RequireJS, which are not available in the browser-based Svelte environment.

To overcome this hurdle, you can consider using a Markdown library that supports modern JavaScript, such as snarkdown. This lightweight Markdown parser works out of the box in a Svelte application, making it a convenient choice for developers.

Another option is to use the svelte-markdown component, which is specifically designed for rendering Markdown content in Svelte. This component eliminates the need to use the potentially unsafe @html directive, providing a safer and more straightforward approach.

Integrating a Markdown Parser into a Svelte Component

Once you have chosen a compatible Markdown parsing library, the next step is to integrate it into your Svelte component. Let's take a look at an example using the marked library:

  import marked from 'marked';

  export let markdownContent;

  let htmlContent = '';

  $: {
    htmlContent = marked(markdownContent, {
      breaks: true,
      sanitize: true,
      smartypants: true,

<div class="markdown-body">
  {@html htmlContent}

  @import 'github-markdown-css/github-markdown.css';

In this example, we import the marked library and create a Svelte component that takes Markdown content as a prop (markdownContent). We then configure the marked library with options to handle line breaks, sanitize the output, and apply smart typography.

The rendered Markdown content is stored in the htmlContent variable, which is updated whenever the markdownContent prop changes. Finally, we use the {@html} directive to render the HTML content within a <div> element styled with the markdown-body class from the GitHub Markdown CSS stylesheet.

Handling Edge Cases and Performance Optimization

While integrating a Markdown parser into your Svelte component is relatively straightforward, there are a few edge cases and performance considerations to keep in mind.

One limitation to be aware of is that some Markdown libraries, such as svelte-markdown, do not support rendering inline HTML within Markdown paragraphs. This is because Svelte handles plain HTML differently compared to other frameworks.

To optimize performance, you can explore techniques like lazy loading or virtual scrolling when rendering large amounts of Markdown content. This can help improve the initial load time and overall responsiveness of your application.

Additionally, it's crucial to sanitize the Markdown content, especially if it comes from an untrusted source, to prevent potential XSS (Cross-Site Scripting) vulnerabilities. Most Markdown parsing libraries offer options to sanitize the output, ensuring that any malicious code is removed before rendering.

Building a Markdown Editor Component in Svelte

To create a Markdown editor component in Svelte, we need to design the user interface, implement real-time preview functionality, add toolbar and formatting options, and handle user input and event listeners. Let's dive into each aspect in detail.

Designing the User Interface for the Markdown Editor

The user interface of the Markdown editor component should consist of two main parts: the input area and the preview area. The input area is where the user writes their Markdown content, while the preview area displays the rendered HTML output.

Here's an example of how the component's structure could look like in Svelte:

<div class="markdown-editor">
  <textarea bind:value={markdownInput} on:input={handleInput}></textarea>
  <div class="preview">
    {@html renderedHTML}

In this example, we have a <div> element with the class markdown-editor that wraps the entire component. Inside it, we have a <textarea> for the user input and a <div> with the class preview to display the rendered HTML.

Implementing Real-time Preview Functionality

To provide a real-time preview of the Markdown content, we need to convert the Markdown input to HTML whenever the user types. Svelte's reactive declarations make this easy to achieve.

First, we need to import a Markdown parsing library like marked or showdown. Then, we can use Svelte's reactive $: syntax to automatically update the renderedHTML whenever the markdownInput changes.

import { marked } from 'marked';

let markdownInput = '';
let renderedHTML = '';

$: renderedHTML = marked(markdownInput);

In this code snippet, we declare two variables: markdownInput to store the user's Markdown input and renderedHTML to store the rendered HTML output. The $: syntax ensures that whenever markdownInput changes, the marked function is called to parse the Markdown and update renderedHTML.

Adding Toolbar and Formatting Options

To enhance the user experience, we can add a toolbar with formatting options to the Markdown editor. The toolbar can include buttons for common Markdown formatting such as bold, italic, headings, lists, and links.

Here's an example of how a toolbar can be added to the component:

<div class="toolbar">
  <button on:click={() => addFormatting('**', '**')}>Bold</button>
  <button on:click={() => addFormatting('*', '*')}>Italic</button>
  <button on:click={() => addFormatting('# ', '')}>Heading 1</button>
  <button on:click={() => addFormatting('- ', '')}>Unordered List</button>
  <button on:click={() => addFormatting('[', '](url)')}>Link</button>

In this example, we have a <div> element with the class toolbar that contains buttons for different formatting options. Each button has an on:click event handler that calls the addFormatting function with the appropriate Markdown syntax.

Handling User Input and Event Listeners

To handle user input and respond to events, we need to bind the markdownInput variable to the <textarea> and listen for the input event.

<textarea bind:value={markdownInput} on:input={handleInput}></textarea>

In this code snippet, we use the bind:value directive to bind the markdownInput variable to the <textarea> value. We also listen for the input event using on:input and call the handleInput function whenever the user types.

The handleInput function can be used to perform any additional processing or validation on the user input before updating the markdownInput variable.

function handleInput(event) {
  // Perform any additional processing or validation
  markdownInput =;

By combining these techniques, we can create a fully functional Markdown editor component in Svelte that provides a seamless editing experience with real-time preview and formatting options.

Syntax Highlighting for Markdown Code Blocks

When rendering Markdown content in a Svelte application, syntax highlighting for code blocks is crucial for enhancing readability and improving the overall user experience. In this section, we'll explore the importance of syntax highlighting, how to integrate syntax highlighting libraries in Svelte, customize highlighting styles, and handle different programming languages.

Importance of Syntax Highlighting in Markdown Rendering

Syntax highlighting is essential when rendering Markdown code blocks because it:

  • Improves code readability by visually distinguishing different elements such as keywords, variables, and comments

  • Enhances the overall presentation of the rendered content, making it more engaging and professional

  • Helps developers quickly identify and understand the structure and syntax of the code snippets

Integrating Syntax Highlighting Libraries in Svelte

To implement syntax highlighting in a Svelte application, you can leverage existing libraries such as PrismJS or highlight.js. Here's an example of how to integrate PrismJS using the mdsvex package:

  1. Install the necessary dependencies:

npm install mdsvex prismjs

  1. Configure mdsvex in your Svelte project's svelte.config.js file:

import { mdsvex } from 'mdsvex';

export default {
  extensions: ['.svelte', '.md'],
  preprocess: mdsvex({
    highlight: {
      highlighter: async (code, lang) => {
        const { default: prism } = await import('prismjs');
        const language = prism.languages[lang];
        return language ? prism.highlight(code, language, lang) : code;
  1. Now you can use Markdown with code blocks in your Svelte components:

  import 'prismjs/themes/prism-tomorrow.css';

# Example Code Block

function greet(name) {
  console.log(`Hello, ${name}!`);

### Customizing Syntax Highlighting Styles

To customize the syntax highlighting styles, you can:

1. Choose a pre-built PrismJS theme CSS file and import it in your Svelte component
2. Create your own custom CSS styles to override or extend the default styles provided by the chosen theme
3. Target specific CSS classes and selectors to fine-tune the appearance of the highlighted code blocks

For example, to change the background color of code blocks:

pre[class*='language-'] {
  background-color: #f4f4f4;

Handling Different Programming Languages

Syntax highlighting libraries like PrismJS support a wide range of programming languages out of the box. To ensure proper highlighting for different languages:

  • Specify the language of each code block using the appropriate language identifier (e.g., js for JavaScript, python for Python)

  • If a language is not supported by default, you can extend the library with additional language definitions or fall back to a generic highlighting style

By following these techniques, you can effectively integrate syntax highlighting for Markdown code blocks in your Svelte application, enhancing the readability and visual appeal of your rendered content.

Creating a Markdown-Powered Blog with Svelte

Svelte provides a powerful and efficient way to create a blog that leverages Markdown for content creation. In this section, we'll explore the process of setting up a Svelte project for a Markdown blog, organizing and storing Markdown files, generating dynamic routes for blog posts, implementing pagination and filtering, and deploying the blog.

Setting Up a Svelte Project for a Markdown Blog

To get started, create a new Svelte project using your preferred method, such as using the Svelte template or SvelteKit. Ensure that you have the necessary dependencies installed, including svelte, svelte-preprocess, and marked (or any other Markdown parser of your choice).

Configure your Svelte project to handle Markdown files by setting up the appropriate loaders and plugins. For example, you can use svelte-preprocess along with marked to preprocess Markdown files and convert them into Svelte components.

Organizing and Storing Markdown Files

Create a dedicated directory within your Svelte project to store your Markdown files. A common convention is to use a directory named posts or blog. Each Markdown file will represent a blog post and should follow a consistent naming convention, such as

Inside each Markdown file, you can include metadata at the top using a format like YAML front matter. This metadata can include properties like the post title, date, author, tags, and any other relevant information you want to associate with the blog post.

Generating Dynamic Routes for Blog Posts

To create individual pages for each blog post, you'll need to generate dynamic routes based on the Markdown files. Svelte provides a powerful routing system that allows you to create dynamic routes easily.

Define a route pattern in your Svelte application that matches the structure of your blog posts. For example, you can use a route like /blog/:slug where :slug represents the unique identifier for each blog post, such as the filename without the extension.

Inside the route component, you can use Svelte's onMount lifecycle function to fetch the corresponding Markdown file based on the slug parameter. Parse the Markdown content, extract the metadata, and render the blog post using Svelte's templating syntax.

Learn more about URL mapping.

Implementing Pagination and Filtering

As your blog grows, you may want to implement pagination and filtering to improve the user experience and performance. Svelte provides several options for handling pagination and filtering.

For pagination, you can create a component that displays a list of blog posts with a limited number of posts per page. Implement navigation controls to allow users to move between pages. You can calculate the total number of pages based on the total count of blog posts and the desired posts per page.

Filtering can be achieved by allowing users to select categories, tags, or other criteria to narrow down the list of blog posts. You can create a component that renders the available filters and updates the displayed blog posts based on the selected filters.

Deploying a Svelte Markdown Blog

Once your Svelte Markdown blog is ready, you can deploy it to a hosting platform of your choice. Svelte applications can be easily deployed to platforms like Netlify, Vercel, or GitHub Pages. Here's a general article on software deployment.

Before deploying, make sure to build your Svelte application using the appropriate build command, such as npm run build or yarn build. This will generate a production-ready version of your application.

Follow the deployment instructions provided by your chosen hosting platform. Typically, you'll need to specify the build output directory and configure any necessary settings, such as custom domains or environment variables.

After deployment, your Svelte Markdown blog will be accessible via a public URL, allowing users to view and interact with your blog posts.

Don't miss the caisy Starter Template to quickly build a blog with SvelteKit and caisy as your Headless CMS.

Best Practices and Advanced Techniques

When working with Markdown rendering in Svelte, there are several best practices and advanced techniques to consider. These approaches can help ensure the security, performance, and flexibility of your Markdown-powered Svelte applications.

Sanitizing User-Generated Markdown Content

One important aspect to keep in mind when rendering Markdown content, especially if it is user-generated, is security. Markdown allows for the inclusion of HTML tags, which can potentially introduce cross-site scripting (XSS) vulnerabilities if not properly sanitized.

To mitigate this risk, it is recommended to use a Markdown parsing library that provides built-in sanitization options. For example, the marked library offers a sanitize option that strips out potentially dangerous HTML tags and attributes. Here's an example of how to enable sanitization with marked:

import marked from 'marked';

const html = marked(markdownContent, { sanitize: true });

Additionally, you can use libraries like DOMPurify to further sanitize the rendered HTML before inserting it into the DOM.

Optimizing Markdown Rendering Performance

Rendering large amounts of Markdown content can impact the performance of your Svelte application. To optimize the rendering process, consider the following techniques:

  • Lazy loading: If your application contains multiple pages or sections with Markdown content, consider implementing lazy loading. Load the Markdown content only when it is needed, rather than rendering everything upfront. This can significantly improve the initial load time of your application.

  • Caching: If the Markdown content remains static or doesn't change frequently, you can cache the rendered HTML. This way, you can avoid re-rendering the same content multiple times, improving performance.

  • Virtual scrolling: For long Markdown documents, implement virtual scrolling techniques to render only the visible portion of the content. This approach reduces the number of DOM elements created and improves rendering performance.

Implementing Lazy Loading for Markdown Content

Lazy loading is a technique that defers the loading of non-critical resources until they are needed. In the context of Markdown rendering in Svelte, you can lazy load Markdown content to improve the initial load time of your application. Here's an example of how to implement lazy loading:

  1. Use dynamic imports to load the Markdown content only when required.

  2. Render a placeholder or loading indicator while the Markdown content is being fetched.

  3. Once the Markdown content is loaded, update the component's state to trigger the rendering of the actual content.

Here's a simplified example:

  let markdownContent = null;

  async function loadMarkdown() {
    const { default: content } = await import('./path/to/');
    markdownContent = content;

{#if markdownContent}
  <MarkdownRenderer {markdownContent} />
  <button on:click={loadMarkdown}>Load Markdown</button>

Customizing Markdown Rendering with Svelte Components

Svelte's component-based architecture allows you to customize the rendering of Markdown elements by creating custom Svelte components. This approach gives you fine-grained control over the appearance and behavior of specific Markdown elements.

For example, you can create a custom component for rendering code blocks with syntax highlighting:

<!-- CodeBlock.svelte -->
  export let language;
  export let code;

<pre class="code-block {language}">

  /* Custom styles for code blocks */

Then, in your Markdown renderer component, you can use the custom CodeBlock component whenever a code block is encountered:

<!-- MarkdownRenderer.svelte -->
  import CodeBlock from './CodeBlock.svelte';

  export let markdownContent;

  function renderCodeBlock({ language, code }) {
    return `<CodeBlock language="${language}" code="${code}" />`;

  {@html marked(markdownContent, { renderer: { code: renderCodeBlock } })}

By leveraging Svelte components for custom rendering, you can create rich and interactive Markdown experiences tailored to your application's needs.


In this comprehensive guide, we've explored the powerful combination of Svelte and Markdown for creating dynamic and interactive web content. Let's recap the key points and discuss future possibilities.

Future Possibilities and Enhancements

The combination of Svelte and Markdown opens up a world of possibilities for future enhancements:

  • Integrating custom Svelte components within Markdown content

  • Implementing collaborative editing features for Markdown documents

  • Exploring advanced parsing techniques for extended Markdown syntax

  • Optimizing performance through lazy loading and caching strategies

As the Svelte ecosystem continues to evolve, we can expect even more powerful tools and libraries to emerge.

Encouraging Readers to Explore Svelte and Markdown Further

If you're a developer looking to create content-rich web applications with ease, Svelte and Markdown are a match made in heaven. By diving deeper into the concepts covered in this guide and experimenting with your own projects, you'll unlock the full potential of this powerful combination.

So, whether you're building a personal blog, a documentation site, or a content management system, Svelte and Markdown provide a solid foundation for creating engaging and interactive web experiences.

In the realm of content management and web development, caisy emerges as a compelling choice for developers seeking a high-performing, user-friendly headless CMS. With its focus on speed, flexibility, and agency workflows, caisy aligns perfectly with the needs of modern developers.

The blueprint functionality in caisy enables the creation of reusable components and standalone documents, empowering developers to build complex designs efficiently. The GraphQL API provided by caisy seamlessly integrates with popular web frameworks like Svelte, allowing developers to create stunning frontends with their preferred technology stack.

Moreover, caisy's scalable multi-tenancy system and comprehensive Digital Asset Management streamline project management, making it an ideal solution for agencies handling multiple clients and projects. The flexible pricing tiers and partnership opportunities further enhance caisy's appeal, catering to projects of various sizes and budgets.

By combining the power of Svelte and Markdown with the capabilities of caisy, developers can unlock new levels of productivity and deliver exceptional web experiences. If you're ready to take your web development game to the next level, sign up for a free caisy account today.

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