Is Klaviyo Slowing Down Your Shopify Store? Here's the Fix

Klaviyo is one of the most popular email marketing platforms for Shopify stores—and for good reason. Its segmentation, automation, and Shopify integration are excellent. But there's a hidden cost: Klaviyo can add 150ms or more to every page load on your store.

For stores where every millisecond matters for conversions, this impact is significant. The good news? You can keep Klaviyo's full functionality while dramatically reducing its performance impact.

Why Klaviyo Slows Down Your Shopify Store

Klaviyo adds JavaScript to your store that does several things:

1. Tracks Visitor Behavior

Klaviyo's tracking script monitors which pages visitors view, what products they look at, and how they navigate your store. This data powers your email segmentation and automation flows.

2. Displays Signup Forms

If you use Klaviyo's embedded forms or popups, additional JavaScript loads to render and manage these elements.

3. Syncs with the Klaviyo Platform

The script makes API calls to Klaviyo's servers to send behavioral data in real-time.

The Problem: Render Blocking

By default, Klaviyo's script loads synchronously in many theme installations. This means the browser waits for Klaviyo's JavaScript to fully download and execute before rendering your page content.

On a 3G mobile connection (which represents a significant portion of shoppers), that 150ms becomes 400ms or more.

The Compound Effect

If you're also running Facebook Pixel (100ms), Google Tag Manager (150ms), and a review app like Yotpo (250ms), you're looking at 650ms of delay before your page even starts rendering—from tracking scripts alone.

How to Check If Klaviyo Is Slowing Your Store

Use Our Free Analyzer

The fastest way to check is with our free Shopify speed analyzer. Enter your URL and we'll:

Detect if Klaviyo is installed
Show you its estimated performance impact
Identify other apps affecting your speed
Provide specific fix recommendations

Check Manually with Chrome DevTools

Open your store in Chrome
Press F12 to open DevTools
Go to the Network tab
Reload the page
Filter by "klaviyo"

You'll see all Klaviyo resources loading. Look at:

Size: How much data Klaviyo adds
Time: How long each resource takes to load
Waterfall: When Klaviyo loads relative to your content

If Klaviyo scripts load before your hero image or main content, they're blocking your Largest Contentful Paint (LCP).

How to Fix Klaviyo's Performance Impact

Option 1: Enable Klaviyo's Async Loading

Klaviyo offers an asynchronous loading option that significantly reduces blocking:

Go to your Klaviyo account
Navigate to Account → Settings → Website Tracking
Look for the async or non-blocking option
Enable it and update your embed code

This change alone can reduce Klaviyo's impact by 50% or more.

Option 2: Defer Loading Until After Page Render

For maximum performance, defer Klaviyo until after your page content loads:

window.addEventListener('load', function() {
  var klaviyoScript = document.createElement('script');
  klaviyoScript.src = 'https://static.klaviyo.com/onsite/js/klaviyo.js?company_id=YOUR_ID';
  klaviyoScript.async = true;
  document.body.appendChild(klaviyoScript);
});

Replace YOUR_ID with your Klaviyo company ID.

This approach loads Klaviyo only after your page is fully rendered, so it doesn't affect your Core Web Vitals scores.

Option 3: Use Our Script Deferrer Snippet

We offer a ready-to-install Liquid snippet that intelligently defers Klaviyo and other marketing scripts. It:

Loads scripts after page render
Maintains full tracking functionality
Works with Klaviyo forms and popups
Handles fallbacks for edge cases

Get your personalized fix →

What About Tracking Accuracy?

Deferred loading means Klaviyo starts tracking a fraction of a second later. For behavioral tracking and email flows, this difference is negligible. Your Browse Abandonment and other automation flows will work exactly the same.

The exception: if you're using Klaviyo for very time-sensitive tracking (like measuring exact time-on-page), you may notice slight differences. For 99% of Shopify stores, this isn't an issue.

Alternatives to Consider

If Klaviyo's performance impact is a dealbreaker, consider these alternatives:

Shopify Email

Shopify's native email marketing is free for up to 10,000 emails/month and adds zero JavaScript to your store. It lacks Klaviyo's advanced segmentation but is perfect for stores prioritizing speed.

Omnisend

Omnisend has a lighter footprint than Klaviyo (around 120ms vs 150ms) while offering similar email and SMS automation features.

Drip

Drip focuses on e-commerce and has built-in performance optimizations. It's particularly good for stores that want powerful automation without heavy JavaScript.

Our Recommendation

For most stores, optimizing Klaviyo is better than switching. Klaviyo's Shopify integration and segmentation capabilities are hard to replace. With proper deferral, you can have both great email marketing and great performance.

The Bottom Line

Klaviyo is a powerful tool, but it doesn't need to slow down your store. With async loading or script deferral, you can reduce its impact by 70% or more while keeping full functionality.

Check if Klaviyo is slowing your store →

Get a free analysis showing Klaviyo's exact impact on your store, plus personalized recommendations to fix it.