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Alex Spinov
Alex Spinov

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Partytown Has a Free API — Run Third-Party Scripts in Web Workers

#javascript #performance #optimization #webdev

What if Google Analytics, Facebook Pixel, and every other third-party script ran in a web worker — freeing your main thread completely?

Partytown by Builder.io moves third-party scripts off the main thread into a web worker.

The Problem

Third-party scripts are the biggest performance killer on most websites. Google Analytics alone adds 30-50ms of main thread blocking. Add Facebook Pixel, HubSpot, Intercom, and hotjar — you lose 200-400ms of interactivity.

Partytown intercepts these scripts and runs them in a web worker. Your main thread stays free for your application code.

How It Works 

<!-- Before: blocks main thread -->
<script src="https://www.googletagmanager.com/gtag/js?id=GA_ID"></script>

<!-- After: runs in web worker -->
<script type="text/partytown" src="https://www.googletagmanager.com/gtag/js?id=GA_ID"></script>
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That's the entire change. Add type="text/partytown" to any script tag.

Framework Integration 

npm install @builder.io/partytown
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Next.js:

import { Partytown } from "@builder.io/partytown/react";

export default function Document() {
  return (
    <html>
      <head>
        <Partytown debug={true} forward={["dataLayer.push"]} />
        <script type="text/partytown" src="https://www.googletagmanager.com/gtag/js" />
      </head>
      <body>{/* ... */}</body>
    </html>
  );
}
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Astro:

---
import { Partytown } from "@builder.io/partytown/astro";
---
<head>
  <Partytown />
</head>
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Real Use Case

An e-commerce site had a Lighthouse performance score of 62 — dragged down by 8 third-party scripts. After adding Partytown, the score jumped to 91. No script was removed, no functionality lost. Main thread blocking time dropped from 340ms to 45ms.

When to Use Partytown

  • Sites with 3+ third-party analytics/marketing scripts
  • E-commerce sites where Core Web Vitals affect SEO
  • Landing pages where every millisecond of load time affects conversion
  • Any site where you cannot remove third-party scripts but need performance

Get Started

Visit partytown.builder.io — open source, works with any framework.

Need custom data pipelines or scraping solutions? Check out my Apify actors or email me at spinov001@gmail.com for custom solutions.

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