How AB Genius loads and why it has no measurable impact on storefront speed.
AB Genius is built for speed
One of the most common concerns merchants have when installing any Shopify app is whether it will slow down their store. Slow pages kill conversions — we know this better than anyone. That’s why AB Genius was engineered from the ground up to have zero measurable impact on your store’s pagespeed.
How AB Genius loads on your store
AB Genius uses a Shopify Theme App Extension to deliver experiments to your storefront.
This means:
No externally injected scripts.
No third-party tags.
No heavy JavaScript frameworks.
The storefront script (ab-live.js) is written in vanilla JavaScript. It has no libraries or dependencies.
It loads asynchronously, so it does not block rendering. Your content, images, and layout load independently of AB Genius.
What happens for visitors NOT in an experiment?
Nothing.
If a visitor is not part of a running experiment, AB Genius does not execute logic, make API calls, or modify page elements. The script detects there’s no active experiment and exits immediately.
That means most traffic experiences zero additional load.
What happens for visitors IN an experiment?
For visitors assigned to an experiment, AB Genius makes a single lightweight API call.
That response contains:
Group assignment.
Price changes, content modifications, or redirect instructions.
Anti-flicker for price tests
For price tests, AB Genius uses anti-flicker technology.
Price elements are hidden with CSS as soon as the script loads. This happens before theme JavaScript runs. The original price never flashes.
Once the correct A/B test price is applied, elements are revealed.
Result: no flashing, no layout shift, no visible swap.
How to verify AB Genius isn’t affecting your pagespeed
Run your store through Google PageSpeed Insights or GTmetrix before and after enabling AB Genius.
In our testing, the difference is negligible. It’s typically within the margin of measurement error.
If you want to be thorough, test with experiments both active and inactive. You should see no meaningful change in Core Web Vitals:
LCP
CLS
INP
Tips for maintaining fast page speeds
AB Genius won’t slow your store down. Your overall performance still matters.
Compress images before uploading. Use TinyPNG or WebP.
Limit apps that inject storefront scripts.
Enable lazy loading for below-the-fold images.
Minimise custom fonts and heavy animations, especially on mobile.
A fast store converts better. Speed is the foundation everything else sits on.
