How to Lazy-Load external scripts for better page speed?

Szymon Soppa

September 9, 2025

Join Elixir newsletter

Subscribe to receive Elixir news to your inbox every two weeks.

Expand your skills

Download free e-books, watch expert tech talks, and explore open-source projects. Everything you need to grow as a developer - completely free.

Explore Community

Table of contents

Nowadays, with an ever-growing number of web services, we tend to overload Web apps with external resources. As a result, it decreases page load speed and affects SEO score. There is a pretty easy solution for that.

Let's assume that you'd like to use the chatbot on your website. Fetching all resources might take in this case, for example, 2 seconds (which is not that unusual - trust me).

Even if your website is fully optimized to load fast, users will still have to wait 2 more seconds for full interaction.

In this case, if you don't need a chatbot to appear immediately, you can lazy-load the script:

setTimeout(function () {
  var d = document,
    s = d.createElement("script");
  s.src = "path-to-js-script";
  d.body.appendChild(s);
}, 5000);

That's it. After 5 seconds, a chatbot will be fetched and attached to the body of your website.

It's important to use a time interval that is long enough to run after the page is fully loaded. In this example, I used 5s interval, but you should use the one that match to your specific case.