App Speed Report · Updated February 2026

Does Omnisend Slow Down Your Shopify Store?

Speed impact analysis of Omnisend (Email & SMS Marketing) — how much it affects your page load time, what scripts it loads, and how to mitigate the performance cost.

Omnisend Speed Impact Summary

Speed Impact Level Medium Impact

Scripts Loaded

175KB

Total Script Size

180-350ms

Avg. Load Time Impact

App Name

Omnisend

How Omnisend Affects Your Store Speed

Omnisend is an email and SMS marketing platform competing with Klaviyo. It loads signup forms, popups, behavioral tracking scripts, and web push notification prompts.

When a visitor lands on your store, Omnisend loads 3 JavaScript files totaling approximately 175KB. These scripts need to be downloaded, parsed, and executed by the browser — all of which takes time and competes with your core page content for network bandwidth and CPU resources.

The measured impact is 180-350ms of additional page load time. To put that in perspective: Google research shows that each additional 100ms of load time reduces conversion rates by up to 7%. If Omnisend adds 180-350ms to your page load, that's a measurable impact on your bottom line.

Omnisend's medium impact means it's contributing noticeably to your load time but isn't the worst offender. Combined with other apps, however, the cumulative effect can be significant.

What These Scripts Do

Omnisend's scripts handle its core email & sms marketing functionality on your storefront. This typically includes:

• Core functionality script — The main JavaScript bundle that powers Omnisend's features on your pages
• Tracking/analytics script — Monitors user interactions and behavior for Omnisend's dashboard and reporting
• UI/widget scripts — Renders visual elements like popups, widgets, or embedded components on your storefront

The problem isn't that these scripts exist — it's that they often load synchronously and on every page, even pages where Omnisend's functionality isn't needed. A visitor browsing your blog doesn't need Omnisend's full email & sms marketing scripts loading and executing.

How to Reduce Omnisend's Speed Impact

You don't have to choose between Omnisend's functionality and a fast store. Here's how to minimize its performance impact while keeping the features you need:

Disable Omnisend's web push notifications if you're not using them — the push prompt loads additional JavaScript

Limit active signup forms to one type (popup OR embedded, not both simultaneously)

Defer Omnisend's tracking script to load after DOMContentLoaded instead of in the head

Disable Omnisend's on-site widgets on mobile if mobile form conversion rates are low

Remove Omnisend's 'Wheel of Fortune' or gamified popups — they're the heaviest campaign type

If you're only using Omnisend for email campaigns (no on-site forms), consider removing the storefront JS entirely

🔍 SEO impact: Reducing Omnisend's speed impact helps your store pass Core Web Vitals — Google's official ranking signal since 2021. Better speed = higher rankings = more organic traffic.

The Bigger Picture: App Bloat on Shopify

Omnisend is just one app on your store. The average Shopify store has 15-25 apps installed, and each one adds its own JavaScript and CSS to your storefront. The cumulative effect is what really kills your speed score.

Think about it: if Omnisend adds 180-350ms and you have 10+ other apps each adding 100-400ms, your total third-party script overhead could be 2-5 seconds. That's the difference between a store that converts and one that loses visitors before the page even loads.

Manually optimizing each app's loading behavior is time-consuming and requires technical knowledge. You'd need to edit theme files, understand JavaScript loading patterns, and constantly monitor for regressions when apps update their scripts.

This is exactly the problem Thunder was built to solve. Thunder automatically scans every app on your store, measures each one's actual speed impact (including Omnisend), and optimizes how they all load — deferring non-essential scripts, reducing blocking time, and ensuring your critical page content loads first.

⚡ See How Omnisend Affects Your Store

Thunder scans your installed apps — including Omnisend — and shows you exactly how much each one impacts your speed. Then it fixes them automatically.

Install Thunder Free →

Free plan available · Scans all your apps · No code changes required

Frequently Asked Questions

Does Omnisend slow down Shopify stores?

Omnisend has a medium speed impact on Shopify stores, typically adding 180-350ms to page load time. It loads 3 scripts totaling approximately 175KB. While this isn't negligible, you can mitigate the impact by deferring its scripts, limiting which pages it loads on, and using a speed optimization app like Thunder to manage its loading behavior.

How much does Omnisend affect my PageSpeed score?

Omnisend typically reduces your PageSpeed Insights mobile score by 3-10 points depending on your store's baseline performance and other installed apps. The 175KB of JavaScript it loads contributes to longer Time to Interactive (TTI) and potentially affects Largest Contentful Paint (LCP) if scripts block rendering. The actual impact varies — stores with fewer apps will notice it more.

Should I uninstall Omnisend to improve speed?

Not necessarily. Omnisend provides valuable functionality (email & sms marketing) that likely benefits your store. Instead of uninstalling, optimize how it loads: defer non-critical scripts, limit it to pages where it's needed, and use Thunder to automatically manage its loading priority. Only uninstall if you're not actively using the app or if the speed cost outweighs the business value.

Can I use Omnisend and still have a fast Shopify store?

Yes. Many high-performing Shopify stores use Omnisend successfully. The key is optimization: don't load Omnisend's scripts on pages where they're not needed, compress your images to offset the script overhead, and use a tool like Thunder to defer Omnisend's JavaScript until after your critical content has loaded. A well-optimized store with Omnisend can still score 80+ on PageSpeed mobile.