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

Technical Q&A

Topic summary

A Shopify store owner reports severe mobile performance issues, with Google PageSpeed Insights showing only 34/100 and load times of 6–20 seconds. The slowdown occurred after installing the Fast Bundle app, raising concerns about its impact on sales, SEO, and user experience.

Community recommendations include:

  • Test with Fast Bundle disabled to isolate whether the app is causing the slowdown
  • Image optimization: Convert to WebP/AVIF format, compress files, and use Shopify’s built-in resizing and CDN
  • App audit: Remove or replace heavy apps; consider consolidating multiple apps into all-in-one solutions
  • Code cleanup: Minify CSS/JS, defer non-essential scripts (tracking, chat widgets), and remove leftover code from uninstalled apps
  • Lazy loading: Enable for off-screen images, videos, and iframes to prioritize above-the-fold content

Multiple respondents requested the store URL for more specific diagnostics. The discussion remains open, awaiting the site link to provide targeted solutions.

Summarized with AI on October 24. AI used: claude-sonnet-4-5-20250929.
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.