Infinite scrolling is a popular UI pattern that allows users to scroll through a large set of data without having to click through pages. Traditionally, implementing infinite scrolling involves JavaScript to detect when the user reaches the bottom of the page and then loading more data. With HTMX, you can avoid writing custom JavaScript while achieving the same functionality using server-side rendering.

In this tutorial, we’ll walk through how to implement infinite scrolling with HTMX, keeping your app fast and lightweight.

Step 1: Set Up the Flask App

Start by creating a simple Flask app that serves the main page and provides an endpoint to load more items as the user scrolls.

First, install Flask if you don’t already have it:

pip install flask

Create a basic Flask app in app.py:

from flask import Flask, render_template, jsonify

app = Flask(__name__)

# Sample data for infinite scrolling
ITEMS = [f"Item {i}" for i in range(1, 101)]

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

@app.route("/load-items/")
def load_items(start):
    # Load a slice of the items based on the 'start' index
    end = start + 10
    items_to_load = ITEMS[start:end]
    return render_template("partials/items.html", items=items_to_load)

if __name__ == "__main__":
    app.run(debug=True)

Step 2: Create the HTML Templates

Create templates/index.html, which will display the initial list of items and set up HTMX to load more content as the user scrolls.

  
  
  
  


  
Infinite Scrolling with HTMX

  

    
Loading items...
  

  

    
Scroll down to load more items...
  



Create templates/partials/items.html:
{% for item in items %}
  
{{ item }}
{% endfor %}

  
  
  Step 3: Add the Infinite Scroll Trigger
The magic of infinite scrolling with HTMX happens in the hx-trigger="revealed" attribute. This triggers the request to load more items when the element becomes visible in the viewport (i.e., when the user scrolls to the bottom).
HTMX listens for the revealed event, which fires when the div containing the hx-get attribute is scrolled into view. This makes it possible to load more data automatically as the user scrolls down the page.

  
  
  Step 4: Run the App and Test
Now, run the Flask app:
python app.py
Visit http://localhost:5000/ in your browser. When you scroll down, new items will automatically load as you reach the bottom of the page. This is accomplished with HTMX without needing any custom JavaScript!
✅ Pros:

🚀 Simple implementation without custom JavaScript
💨 Fast server-side rendering with Flask
📦 Light and efficient: avoid bloated frontend frameworks
⚠️ Cons:

🌐 Requires a reliable server-side endpoint for fetching data
🧱 Might not be suitable for very large datasets (pagination or lazy-loading optimizations may be needed)

  
  
  Summary
In this tutorial, we implemented infinite scrolling using HTMX with Flask, allowing us to load new content as the user scrolls without writing a single line of JavaScript. HTMX makes it easy to create dynamic, user-friendly interfaces while keeping your app lightweight and SEO-friendly.
📘 Want to learn more about HTMX?
To go deeper into HTMX and learn how to build more advanced web apps without JavaScript frameworks, grab my 24-page PDF tutorial for just $10:
👉 HTMX Tutorial: Build Modern Web Apps Without JavaScript Frameworks
If you found this helpful, consider buying me a coffee: Buy Me a Coffee ☕