Fix Mermaid ELK Layouts Not Activated In Docusaurus

Jul 28, 2025 by Sharif Sakr 52 views

Mermaid ELK Layouts Not Activated in Docusaurus: A Solution Guide

Hey guys! Ever run into a snag where your Mermaid diagrams in Docusaurus just aren't laying out the way you expect? Specifically, when you're trying to use the ELK layout engine? Yeah, it can be a real head-scratcher. But don't worry, we're gonna dive deep into this issue and figure out a solid solution. This guide is designed to help you understand why your Mermaid ELK layouts might not be activating in Docusaurus and, more importantly, how to fix it. Let's get started!

Understanding the Issue

So, you've been working with Docusaurus, the awesome static site generator, and you're trying to integrate Mermaid diagrams, which are fantastic for visualizing complex systems and processes. You've heard about the ELK (Eclipse Layout Kernel) layout engine, which promises to provide more sophisticated and visually appealing layouts compared to the default Dagre engine. You even added the config block in your Mermaid code, specifying layout: elk. But alas, nothing seems to change! Your diagrams stubbornly stick to the old layout, leaving you wondering what's going on.

What's ELK and Why Use It?

Before we go further, let's quickly touch on what ELK is and why you might want to use it. ELK is an open-source layout kernel that offers advanced layout algorithms for various diagram types. It's particularly good at handling complex graphs and networks, producing layouts that are both readable and aesthetically pleasing. For instance, in ER diagrams or network graphs, ELK can help minimize edge crossings, reduce node overlaps, and create a more balanced visual representation. This is why specifying ELK can be a game-changer for those intricate diagrams, but only if it actually works!

The Docusaurus-Mermaid Connection

Docusaurus supports Mermaid out of the box, which is super convenient. You can easily embed Mermaid diagrams in your Markdown files, and Docusaurus will handle the rendering. However, the integration isn't always seamless, especially when it comes to advanced features like ELK layouts. Docusaurus relies on the Mermaid library to render the diagrams, and if certain components or configurations are missing, things might not work as expected. This is precisely what's happening with the ELK layout issue.

The Root Cause: Missing ELK Integration

The core problem lies in the fact that Docusaurus, by default, doesn't include the necessary component to enable ELK layouts in Mermaid. The official Mermaid documentation on GitHub highlights that web frameworks using Mermaid should incorporate the @mermaid-js/layout-elk package. This package contains the ELK layout engine and its dependencies. Without this, Mermaid simply doesn't know how to process the layout: elk configuration, and it falls back to the default Dagre layout. It's like telling your car to fly – it has the instruction, but it lacks the wings!

Why This Matters

So, why is this a big deal? Well, for simple diagrams, the default Dagre layout might suffice. But when you're dealing with complex relationships and a large number of nodes, the layout can become cluttered and hard to follow. ELK offers a way to create more organized and visually clear diagrams, which can significantly improve the communication of your ideas. Imagine trying to explain a complex system architecture with a messy diagram – not fun, right? ELK can help you avoid that visual chaos.

Diagnosing the Problem

Okay, so we know what the problem is in theory. But how do you confirm that you're actually facing this issue in your Docusaurus project? Here are a few steps you can take to diagnose the situation:

Step 1: Check Your Mermaid Configuration

First things first, let's make sure you've actually configured Mermaid to use the ELK layout. This typically involves adding a config block at the beginning of your Mermaid diagram, like this:

---
config:
 layout: elk
---
erDiagram
 COMPANY ||--o{ DEPARTMENT : has
 // ... rest of your diagram

Ensure that the layout: elk line is present and correctly spelled. A simple typo can prevent the ELK layout from being activated. Also, make sure this config block is at the very beginning of your Mermaid code block.

Step 2: Compare with Mermaid Live Editor

A great way to verify that your diagram is supposed to work with ELK is to try it out in the official Mermaid Live Editor. This online editor has full support for ELK layouts, so if your diagram looks correct there, it's a good indication that the issue lies within your Docusaurus setup. Paste your Mermaid code into the editor and see if the ELK layout is applied as expected. If it looks good in the editor but not in Docusaurus, you've likely pinpointed the problem.

Step 3: Inspect the Rendered Diagram

When your Docusaurus site is running, inspect the HTML and JavaScript in your browser's developer tools. Look for the Mermaid code and how it's being rendered. You might be able to spot some clues about why the ELK layout isn't being applied. For example, you might see error messages in the console related to missing dependencies or failed layout attempts. This can give you a more concrete understanding of what's going wrong behind the scenes.

Step 4: Replicate the Issue in a Minimal Setup

If you're still unsure, try creating a minimal Docusaurus site with just a single page containing your Mermaid diagram. This helps isolate the issue from any other configurations or customizations in your main project. If the ELK layout still doesn't work in this minimal setup, you can be pretty confident that it's a general integration problem rather than a conflict with other parts of your site.

The Solution: Installing and Configuring `@mermaid-js/layout-elk`

Alright, we've diagnosed the problem, and now it's time for the fun part: fixing it! The solution involves installing the @mermaid-js/layout-elk package and configuring Docusaurus to use it. Here's a step-by-step guide:

Step 1: Install the `@mermaid-js/layout-elk` Package

First, you'll need to install the @mermaid-js/layout-elk package as a dependency in your Docusaurus project. Open your terminal, navigate to your project directory, and run the following command using either npm or yarn:

npm install @mermaid-js/layout-elk

Or, if you're using yarn:

yarn add @mermaid-js/layout-elk

This command will download and install the package, adding it to your project's node_modules directory and updating your package.json file. This is a crucial step – without this package, Mermaid simply won't have the ELK layout engine available.

Step 2: Configure Docusaurus to Use the ELK Layout

Next, you need to tell Docusaurus to actually use the @mermaid-js/layout-elk package. This typically involves modifying your Docusaurus configuration file (docusaurus.config.js or docusaurus.config.ts). You'll need to import the package and configure Mermaid to use it. Here's how you can do it:

Import the ELK layout:

At the beginning of your configuration file, add the following import statement:
```
const mermaid = require('mermaid');
const { ElkExtendedServices } = require('@mermaid-js/layout-elk');
```
This imports the necessary modules from the @mermaid-js/layout-elk package.
Configure Mermaid:

Within your Docusaurus theme configuration, you'll need to configure the Mermaid plugin to use the ELK layout. This usually involves adding a mermaid option to your theme configuration. Here's an example of how it might look:

   presets: [
   [
   '@docusaurus/preset-classic',
   {
   theme: {
   customCss: require.resolve('./src/css/custom.css'),
   },
   },
   ],
   ],
   themeConfig: {
   mermaid: {
     options: {
       elk: {},
     },
   },

This tells Docusaurus that you want to use the ELK layout engine for Mermaid diagrams. The empty object {} in the elk configuration signifies that you're using the default ELK settings, but you can customize these settings further if needed.

Restart Your Docusaurus Server:

After making these changes, you'll need to restart your Docusaurus development server for the new configuration to take effect. Stop the server (usually by pressing Ctrl+C in your terminal) and then start it again using npm start or yarn start. This ensures that Docusaurus picks up the changes you've made to the configuration file.

Step 3: Verify the ELK Layout

With the @mermaid-js/layout-elk package installed and Docusaurus configured, it's time to verify that the ELK layout is working correctly. Open your Docusaurus site in your browser and navigate to the page containing your Mermaid diagram. If everything is set up correctly, you should now see the diagram rendered with the ELK layout engine. This means that the layout should be more organized, with fewer edge crossings and a more balanced visual representation.

Step 4: Fine-Tuning (Optional)

If you want to further customize the ELK layout, you can explore the various configuration options available in the @mermaid-js/layout-elk package. These options allow you to control aspects such as node spacing, edge routing, and overall layout style. Refer to the ELK documentation for a full list of available options and how to use them. You can pass these options within the elk object in your Docusaurus configuration, like this:

   presets: [
   [
   '@docusaurus/preset-classic',
   {
   theme: {
   customCss: require.resolve('./src/css/custom.css'),
   },
   },
   ],
   ],
   themeConfig: {
   mermaid: {
     options: {
       elk: {
         direction: 'RIGHT',
         spacing: 100,
       },
     },
   },

This example sets the layout direction to RIGHT and increases the spacing between nodes to 100 pixels.

Troubleshooting Common Issues

Even with the steps outlined above, you might still encounter some issues. Here are a few common problems and how to troubleshoot them:

Issue 1: ELK Layout Still Not Applied

If the ELK layout isn't being applied even after following the steps, double-check your configuration file for any typos or syntax errors. A small mistake can prevent the configuration from being parsed correctly. Also, ensure that you've restarted your Docusaurus server after making the changes. Sometimes, the server might not pick up the new configuration until it's restarted.

Issue 2: Errors in the Browser Console

Check your browser's developer console for any error messages related to Mermaid or ELK. These messages can provide valuable clues about what's going wrong. For example, you might see errors indicating that the @mermaid-js/layout-elk package is not found or that there's a problem with the Mermaid configuration. Addressing these errors directly can often resolve the issue.

Issue 3: Diagram Looks Distorted or Overlapping

If the ELK layout is being applied but the diagram looks distorted or nodes are overlapping, you might need to adjust the ELK configuration options. Experiment with different spacing and layout directions to find settings that work well for your specific diagram. The default ELK settings might not be optimal for all diagrams, so some fine-tuning might be necessary.

Issue 4: Conflict with Other Plugins or Themes

In rare cases, there might be a conflict between the @mermaid-js/layout-elk package and other plugins or themes in your Docusaurus project. If you suspect this is the case, try temporarily disabling other plugins or themes to see if that resolves the issue. If it does, you can then investigate the specific conflict and find a workaround.

Real-World Examples and Use Cases

To give you a better sense of when and why you might want to use ELK layouts in your Docusaurus documentation, let's look at some real-world examples and use cases:

Example 1: Entity-Relationship Diagrams (ERDs)

As we saw in the initial problem description, ERDs are a classic use case for ELK layouts. ERDs often involve complex relationships between entities, and the default Dagre layout might not always produce the clearest visualization. ELK can help organize the entities and relationships in a more structured and readable way, making it easier to understand the database schema.

Example 2: Network Diagrams

If you're documenting a network architecture, ELK can be invaluable for creating clear and informative diagrams. Network diagrams often involve numerous nodes and connections, and ELK's advanced layout algorithms can help minimize clutter and highlight the key relationships between network components.

Example 3: Flowcharts and Process Diagrams

ELK can also be used to improve the layout of flowcharts and process diagrams. By optimizing the arrangement of nodes and edges, ELK can make it easier to follow the flow of a process and identify potential bottlenecks or inefficiencies.

Example 4: State Diagrams

State diagrams, which are used to model the behavior of systems over time, can also benefit from ELK layouts. ELK can help organize the states and transitions in a logical and visually appealing manner, making it easier to understand the system's behavior.

Conclusion

So, there you have it! We've walked through the issue of Mermaid ELK layouts not activating in Docusaurus, diagnosed the problem, and provided a step-by-step solution. By installing the @mermaid-js/layout-elk package and configuring Docusaurus to use it, you can unlock the power of ELK and create more organized and visually appealing diagrams in your documentation. Remember, clear diagrams are essential for effective communication, and ELK can be a valuable tool in your documentation arsenal.

If you've been struggling with this issue, I hope this guide has been helpful. And if you have any further questions or run into any other problems, don't hesitate to reach out. Happy diagramming, guys!