Stop loading
everything at once.

Boostify is a JavaScript toolkit that defers scripts, loads resources on demand, and keeps your main thread free — so your site feels instant.

Get Started View on GitHub

↓ 78%

bundle size reduction

↑ 40pts

Lighthouse score improvement

< 1kb

gzip core size

The Problem

Third-party scripts are killing your Core Web Vitals.

Most devs load everything on page load — analytics, chat widgets, video embeds — even when the user never scrolls that far. Every script competes for your main thread, blocking your actual content from appearing. Boostify gives you back control.

Blocked main thread

Scripts fight for CPU time with your content, making your site unresponsive on load.

Inflated bundle size

Third-party scripts add hundreds of kBs users must download before seeing anything.

Slow LCP & FID

Google penalizes slow Core Web Vitals — which directly impacts your search rankings.

How it works

Up and running in minutes

Install Boostify

Add it to your project in seconds. Works with any framework or plain HTML.

Choose your trigger

Pick when to load: on scroll, click, element visibility, user inactivity, or page load.

Load only what's needed

Scripts, styles, and videos load precisely when the user needs them — not before.

Real-world examples

See it in action

Google Analytics fires on every page load — even for bots and bounces that never convert. Defer it until the browser is idle and the user has actually engaged, so your Core Web Vitals stay clean and your data stays meaningful.

const bstf = new Boostify({ debug: false });

// Mark scripts with type="text/boostify" in your HTML:
// <script type="text/boostify" src="gtag.js"></script>

bstf.onload({
  worker: true,    // load via proxy (recommended)
  callback: (result) => {
    console.log('Analytics ready!', result.triggeredBy);
  }
});

Chat widgets, sticky banners, and newsletter pop-ups have no business loading before the user has even read a single line. Wait until they scroll 400px — then load. Your LCP will thank you.

const bstf = new Boostify();

bstf.scroll({
  distance: 400,
  callback: async () => {
    await bstf.loadScript({
      url: 'https://cdn.example.com/chat-widget.js',
      appendTo: 'body',
    });
  }
});

Why load Stripe.js on every page when only 5% of visitors ever reach the pricing section? The Intersection Observer watches for the element — and only then pulls in the script, saving ~100kb of JavaScript for everyone else.

const bstf = new Boostify();

bstf.observer({
  element: document.querySelector('#pricing-section'),
  options: { threshold: 0.1 },
  callback: async () => {
    await bstf.loadScript({
      url: 'https://js.stripe.com/v3/',
      appendTo: 'head',
    });
    const stripe = Stripe('pk_live_...');
  }
});

A video embed sitting below the fold has no reason to block your main thread. Watch the container enter the viewport, then inject the player — zero layout shift, zero wasted bandwidth for users who never scroll that far.

const bstf = new Boostify();

// HTML: <div class="js--video" style="aspect-ratio:16/9"></div>

bstf.observer({
  element: document.querySelector('.js--video'),
  options: { threshold: 0.01 },
  callback: () => {
    bstf.videoPlayer({
      url: { mp4: '/videos/demo.mp4' },
      attributes: { controls: true, muted: true, autoplay: true },
      appendTo: document.querySelector('.js--video'),
    });
  }
});

HubSpot, Intercom, Drift — support chat scripts are some of the heaviest third-party payloads you can load. Fire them only after 5 seconds of inactivity, when the user is clearly idle and ready to engage. PageSpeed never sees them.

const bstf = new Boostify();

// HubSpot loads only after 5s of inactivity
bstf.inactivity({
  idleTime: 5000,
  name: 'hubspot-loader',
  callback: async () => {
    await bstf.loadScript({
      url: '//js.hs-scripts.com/YOUR_PORTAL_ID.js',
      appendTo: 'body',
      attributes: ['id=hs-script-loader', 'async', 'defer'],
    });
  }
});

Features

Free. Open source. No limits.

Boostify is completely free to use. No licenses, no hidden plans. Just a fast, focused toolkit for developers who care about performance.

Read the Docs Star on GitHub

Stop loading
everything at once.

Third-party scripts are killing your Core Web Vitals.

Blocked main thread

Inflated bundle size

Slow LCP & FID

Up and running in minutes

Install Boostify

Choose your trigger

Load only what's needed

See it in action

Everything you need to go fast

Trigger: On Load

Trigger: On Scroll

Trigger: Observer

Trigger: Inactivity

Content Injection

Video Embed

Free. Open source. No limits.

Stop loading everything at once.

Third-party scripts are killing your Core Web Vitals.

Blocked main thread

Inflated bundle size

Slow LCP & FID

Up and running in minutes

Install Boostify

Choose your trigger

Load only what's needed

See it in action

Everything you need to go fast

Trigger: On Load

Trigger: On Scroll

Trigger: Observer

Trigger: Inactivity

Content Injection

Video Embed

Free. Open source. No limits.

Stop loading
everything at once.