Setting Up a Flask-FlatPages Blog with Server-Side KaTeX Rendering

I set out to create a blog using Flask-FlatPages to display numerous mathematical equations, like the Quadratic Formula and Pythagorean Theorem, rendered server-side for consistency. On my Linux system, I used the markdown-katex package, which includes KaTeX’s binary engine, so I didn’t need Node.js. I also wanted to know if a KaTeX CSS style file was necessary and what would happen without one. Here’s how I got it working.

Configuring Flask-FlatPages with markdown-katex

I started by installing markdown-katex, which includes KaTeX’s binary engine for Linux, avoiding the need for Node.js.

pip install markdown-katex

I verified the installation to confirm it was ready.

python -m markdown_katex --version

This showed a version like v202406.1035, confirming markdown-katex was set.

I updated my Flask app (app.py) to integrate markdown-katex with Flask-FlatPages.

from flask import Flask, render_template
from flask_flatpages import FlatPages
import logging

app = Flask(__name__)
app.config['FLATPAGES_AUTO_RELOAD'] = True
app.config['FLATPAGES_EXTENSION'] = '.md'
app.config['FLATPAGES_ROOT'] = 'pages'
app.config['FLATPAGES_MARKDOWN_EXTENSIONS'] = ['markdown_katex']
app.config['FLATPAGES_EXTENSION_CONFIGS'] = {
    'markdown_katex': {
        'insert_fonts_css': True
    }
}
pages = FlatPages(app)

logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)

@app.route('/<path:path>')
def page(path):
    logger.debug(f"Rendering page: {path}")
    page = pages.get_or_404(path)
    return render_template('post.html', post=page)

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/pages')
def list_pages():
    return "<br>".join(page.path for page in pages)

if __name__ == '__main__':
    app.run(debug=True, port=5000)

The insert_fonts_css: True embedded KaTeX CSS in the HTML output, eliminating the need for a separate style file.

Style File Considerations

I wondered if markdown-katex required a CSS style file and what would happen without one.

With insert_fonts_css: True, KaTeX CSS is automatically included in the HTML, ensuring equations render with proper math fonts (e.g., Cambria Math) without a separate file.

I chose insert_fonts_css: True for simplicity and consistent styling.

If I set insert_fonts_css: False and omitted the CSS, equations would still render as HTML but might use default browser fonts, leading to inconsistent or plain formatting.

Testing Equation Rendering

I created a test Markdown file (pages/math-test.md) to verify rendering.

---
title: Math Test
date: 2025-08-24
tags: [math, katex]
category: Technology
---
Inline math: $`x^2 + y^2 = z^2`$
Block math:
```math
E = mc^2
```

I visited http://localhost:5000/math-test and confirmed equations rendered as $x^2 + y^2 = z^2$ and $E = mc^2$ . The embedded CSS ensured proper styling.

Conclusion

Using markdown-katex with its built-in KaTeX binary on my Linux system, I successfully set up server-side equation rendering for my Flask-FlatPages blog. The insert_fonts_css: True setting streamlined styling, and my blog now displays mathematical equations consistently, like the Pythagorean Theorem and Quadratic Formula. I’ll continue adding content and refining the setup as needed.

References

Disclaimer: This blog post was created with assistance from Grok 3, an AI developed by xAI, under my direct supervision and guidance to ensure accuracy and alignment with my vision for the content.