Help Needed: Shopify Site Speed Issues (Mobile Performance Very Low)

Technical Q&A
1

Hi there,

We’re urgently looking to improve our store’s performance. Recently, we noticed a significant slowdown, especially on mobile, Google PageSpeed Insights is showing a score of only 34/100, with pages taking 6–20 seconds to load. Since most of our customers shop on their phones, this is a major issue for sales, SEO rankings, and overall customer experience.

We recently installed Fast Bundle as our bundle app, and it’s possible this has contributed to the slowdown. How can we get to optimise the site for faster performance?

Thank you!

2

Hi @FranZN ,
I hope this message finds you well.
Test site speed with Fast Bundle disabled.
Compress all images to WebP and use Shopify resizing.
Audit apps → remove or replace heavy ones.
Move any non-essential scripts to load defer.
Thanks
Manoj

3

Hard to tell without seeing your site. Share a link to your store to get more specific suggestions.

4

Hi @FranZN,

Please send the website link, I will check it for you

5

Usually, the cause code of slow speed on phone is due to large elements existing on a store, such as large size images, JS codes and apps or plugs installed recently. But it depends here and need to further check by checking the website details in real.

Please remember to share store URL with this kind of questions raised next time.

6

love to help! please share your store url.

8

Hello @FranZN ,

I hope you are doing well!

You can check the following points and fix themimmideatly for SEO:

Image Optimization

  • Compress images (WebP/AVIF) without losing quality.

  • Use responsive image sizes (different resolutions for mobile/desktop).

  • Shopify’s built-in CDN helps, but ensure original uploads are optimized.

  1. Lazy Loading

    • Enable lazy loading for all off-screen images, videos, and iframes.

    • Prioritize above-the-fold content to load first.

  2. Minify & Defer Scripts

    • Minify CSS/JS and inline critical CSS.

    • Defer non-essential scripts (e.g., tracking, chat widgets, review widgets) to load after page render.

  3. Reduce App Bloat

    • Audit all installed Shopify apps.

    • Remove or replace heavy apps (many inject large JS/CSS).

    • Where possible, replace with all-in-one apps (like AiTrillion for email, SMS, reviews, loyalty instead of multiple separate apps).

9

From what I know, clearing unnecessary codes left from uninstalled apps and removing less important plugins can make the site faster.

10

Hi, @FranZN

Mobile performance issues are usually related to how assets are loaded on the storefront rather than a single system-level problem.

A few core areas usually help improve performance in a measurable way.

Optimize images and initial content
Ensure images are uploaded at the size they’re displayed on mobile and avoid loading large visuals in the first viewport unless they’re essential. Using explicit dimensions helps prevent layout shifts and improves perceived load speed.

<img

src=“/images/product.jpg”

alt=“Product image”

width=“800”

height=“600”

loading=“lazy”

decoding=“async”>

Reduce render-blocking scripts
Non-critical scripts such as analytics, reviews, or chat tools should not block the initial render. Deferring these scripts allows the page to load content first and execute scripts afterward.

Fonts and styling
Limit font families and weights to what’s required. Fewer font requests speed up text rendering on mobile connections.

After applying these changes, test again with PageSpeed Insights or Lighthouse to confirm improvements to Core Web Vitals.

Alternatively, if you don’t prefer not to handle performance optimization manually Website Speedy, helps identify and optimize assets that affect mobile load performance.

( Disclosure: We are the developers of Website Speedy and are happy to assist if needed.)