Front Matter CMS Preview Configuration

Simplified Front Matter CMS preview wiring for IT-Journey — a `/preview///` directory pattern that survives custom Jekyll permalinks.

• bamr87
• Published Apr 25, 2024
• Updated May 24, 2026
• Tools
• frontmatter jekyll preview cms tooling
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Table of Contents

Front Matter Preview Configuration

This directory contains the implementation for simplified Front Matter CMS preview functionality in the IT-Journey repository.

Overview

The goal was to create a systematic way to link the FrontMatter CMS preview button with Jekyll-generated content, providing a consistent and reliable preview experience during development.

Solution Implemented

Instead of trying to handle Jekyll’s complex permalink logic within FrontMatter’s templating system, we implemented a simplified preview directory structure that:

1. Standardizes all preview URLs to /preview/<collection>/<filename>/
2. Automatically generates preview directories during Jekyll build
3. Works consistently regardless of custom permalinks or Jekyll collection settings

Components

1. FrontMatter Configuration (frontmatter.json)

Updated the frontMatter.content.pageFolders configuration to use a simple, consistent preview path structure:

{
  "title": "posts",
  "previewPath": "/preview/posts//",
  "path": "[[workspace]]/pages/_posts",
  "contentTypes": ["default"]
}

Key Template Variables:

• `` - The filename without extension (e.g., “2025-10-19-test-post”)
• Collection name is hardcoded in the path for consistency

2. Jekyll Preview Generator Plugin (_plugins/preview_generator.rb)

A custom Jekyll plugin that runs during the build process to create the preview directory structure:

Features:

• Runs only in development environment (JEKYLL_ENV=development)
• Processes all Jekyll collections (posts, quests, docs, notes, etc.)
• Creates /preview/<collection>/<filename>/index.html for each document
• Copies the fully rendered HTML content to each preview directory
• Provides detailed logging for debugging

Example Generated Structure:

_site/
  preview/
    posts/
      2025-10-19-test-post/
        index.html
    quests/
      2023-11-23-begin-your-it-journey/
        index.html
    docs/
      example-documentation/
        index.html

Usage

For Content Creators

1. Open any markdown file in VS Code within the configured collections
2. Click the FrontMatter “Open Preview” button
3. Preview opens at http://localhost:4002/preview/<collection>/<filename>/

For Developers

The preview URLs follow a predictable pattern:

• Posts: /preview/posts/<filename>/
• Quests: /preview/quests/<filename>/
• Docs: /preview/docs/<filename>/
• Notes: /preview/notes/<filename>/
• About: /preview/about/<filename>/
• Quickstart: /preview/quickstart/<filename>/

Benefits

✅ Advantages of This Approach

1. Simplicity: No complex templating logic in FrontMatter configuration
2. Reliability: Works regardless of Jekyll permalink settings
3. Consistency: All preview URLs follow the same pattern
4. Performance: Direct file access, no Jekyll routing logic needed
5. Debugging: Easy to troubleshoot with predictable URLs
6. Development Focus: Optimized for development workflow, not production

🔄 Trade-offs

1. Development Only: Preview structure only exists during development builds
2. Disk Space: Creates duplicate HTML files for preview purposes
3. Build Time: Slight increase in Jekyll build time due to file copying
4. URL Differences: Preview URLs differ from production URLs

Configuration Details

Environment Requirements

• Jekyll Environment: Must be set to development
• Docker Setup: Works with the existing Docker-based Jekyll environment
• Port: Jekyll server running on localhost:4002

FrontMatter Template Variables Available

• `` - Filename without extension
• `` - Relative file path
• `` - URL-friendly slug
• `` - Date formatting (for posts)

Troubleshooting

Preview Directory Not Created

1. Check Jekyll environment: docker-compose exec jekyll env | grep JEKYLL_ENV
2. Verify plugin logs in Docker output: docker-compose logs jekyll
3. Ensure development config is loaded: _config.yml,_config_dev.yml

Preview Button Not Working

1. Verify FrontMatter configuration in frontmatter.json
2. Check file is in configured collection path
3. Ensure Jekyll server is running on port 4002
4. Test URL manually: http://localhost:4002/preview/<collection>/<filename>/

Plugin Not Running

1. Check plugin file exists: _plugins/preview_generator.rb
2. Verify Jekyll can load plugins (development mode)
3. Look for plugin output in logs: Preview Generator: Hook triggered!

Testing

A test file is included: pages/_posts/2025-10-19-test-frontmatter-preview.md

Test Steps:

1. Open the test file in VS Code
2. Click FrontMatter preview button
3. Should open: http://localhost:4002/preview/posts/2025-10-19-test-frontmatter-preview/
4. Verify content renders correctly

Future Enhancements

Potential improvements for this system:

1. Conditional Logic: Add support for custom permalinks when defined
2. Production Mode: Adapt for production environments if needed
3. Performance: Optimize file copying for large collections
4. Caching: Implement intelligent rebuilding for changed files only
5. Integration: Enhanced integration with other development tools

Related Files

• /frontmatter.json - FrontMatter CMS configuration
• /_plugins/preview_generator.rb - Jekyll plugin for preview generation
• /_config_dev.yml - Development configuration
• /docker-compose.yml - Development environment setup

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This implementation provides a robust, maintainable solution for FrontMatter preview functionality that prioritizes developer experience and reliability over complexity.