Shopify Page Speed Stuck Low? Fix the App Scripts First

If your Shopify page speed score barely moved after you compressed images, the cause is render-blocking JavaScript from your installed apps, not your images. The fix is to audit every app in Shopify Admin, uninstall the ones you do not actively use, and then manually remove the leftover code each app injected into your theme files. Image optimization rarely moves a mobile score until app scripts are dealt with first.

Marcus runs a small grilling-supplies store on the Dawn theme. He spent a weekend compressing every product image to under 200KB, switched everything to WebP, and ran PageSpeed Insights on his iPhone. His desktop score climbed to 78. Mobile sat at 34. He had 13 apps installed over two years, including a chat widget he had forgotten about and a review tool he replaced six months ago. The leftover code from both was still firing on every page load.

Why isn't my Shopify page speed improving after I optimized images?

Image optimization is the first thing every guide tells you to do, and it does help on desktop. On mobile, though, the bottleneck is rarely image weight. It is JavaScript execution time. Compressing a 1MB hero image down to 200KB shaves a few hundred milliseconds. A single app that injects a 400KB script onto every page can add five seconds.

A developer scraped public performance data from more than 10,000 Shopify stores in March 2026. The average mobile score across all of them was 54 out of 100, and 32.68% sat below 50. Largest Contentful Paint averaged 12.3 seconds on mobile, almost five times Google's 2.5-second threshold for a "good" rating. Each installed app correlated with a 0.48-point drop in the mobile score. Stores running 10 or more apps averaged 39 on mobile. Stores with no apps averaged 75.

Google does not test your store on your iPhone. Its crawler simulates a mid-range Android device on 4G, the conditions that match how the majority of mobile shoppers actually browse. So when you open your store on Gigabit Wi-Fi and a $1,500 phone and it feels fast, you are testing in a setting that does not exist in the real shopping pipeline. Run pagespeed.web.dev against your homepage and a product page and look at the mobile column. That is the only number that matters for shopify page speed and Core Web Vitals ranking.

How do I find which apps are slowing down my store?

Open Shopify Admin > Apps. Make a list. For each app, ask yourself one question: am I actively using this in the last 30 days? Anything you cannot answer "yes" to is a candidate for removal.

Then go to Online Store > Themes > Speed report. Shopify lists which apps contribute the most load time, ranked. Treat that list as your priority order. The top item is almost always something you can replace with a lighter alternative or remove entirely.

Now run a controlled isolation test:

1. Run pagespeed.web.dev on your homepage and one product page. Note the mobile scores.
2. Uninstall one app from your candidate list.
3. Wait 30 minutes for the CDN cache to clear.
4. Re-run pagespeed.web.dev on the same two URLs.
5. Note the difference. Anything over a 3-point gain on mobile is significant.
6. Repeat with the next app.

This sounds slow. It is, and that is the point. Removing five apps in one batch tells you the total impact. Removing them one at a time tells you which one was actually the problem, so you do not accidentally reinstall a useful tool that was not the cause. One r/shopify post documented a store where removing two of three recently-installed apps brought conversion from below average back to 2.8% within days, and one of those apps alone was responsible for 400ms of load time.

How do I remove an app's leftover code from my theme?

Uninstalling an app from Shopify Admin does not remove the code that app injected into your theme. This is the single biggest reason merchants report no improvement after uninstalling. Snippets stay in theme.liquid. Asset files stay in your theme's Assets folder. Embedded JavaScript tags keep firing.

Before you touch theme code, duplicate your theme. Online Store > Themes > Actions > Duplicate. Work on the copy, preview it, and publish only after you verify nothing is broken.

To clean up residual code:

1. Go to Online Store > Themes > Edit code on your duplicated theme.
2. Open theme.liquid and search (Cmd+F or Ctrl+F) for the app's name. Common patterns: the app's brand name, the developer's name, or a snippet ID. Delete any matching <script> blocks or {% include %} lines.
3. Open every file under Templates, Sections, Snippets, and Layout. Search each for the app name. Delete what you find.
4. Open the Assets folder. Look for any .js, .css, or .liquid files named after the app. Delete them.
5. Check Config > settings_data.json for any leftover config blocks. Delete any orphaned sections that no longer match anything in your theme.

If you do not remember which apps you installed, the search-by-name approach falls apart. In that case, look for <script> tags in theme.liquid that load from external domains other than cdn.shopify.com. Each one is a third-party script. Comment one out at a time, preview the store, and confirm nothing visible breaks before you delete it.

The Shopify Community thread "Slow Store Speed" from a merchant who uninstalled 10 apps in one go is a textbook example: their store stayed slow for weeks because none of the leftover code came out with the apps. They had to clean it manually, file by file.

What about speed optimizer apps, do they actually help?

Be skeptical. A speed optimizer app is itself a script that runs on every page load. The honest test is whether it removes more load time than it adds, and most merchants who post before-and-after numbers in public threads either show negligible gains or are the developers of those apps.

Here is the comparison most merchants run into:

Approach	Load time impact	Effort	Notes
Compress images to WebP	-300ms typical	Low (1-2 hours)	Easy win, but rarely moves mobile score by more than 5 points
Remove unused apps	-1 to -5 seconds	Medium (2-4 hours)	Highest impact for stores with 8+ apps
Clean residual app code	-500ms to -2 seconds	Medium-high (3-6 hours)	Required after uninstalls; otherwise the gain is partial
Install a "speed optimizer" app	Variable, often net-zero	Low	Adds a script to remove other scripts; rarely a clear win
Replace page builder with native theme	-2 to -3 seconds	High (rebuild pages)	One merchant went from 5s to 2.5s by swapping a page-builder header/footer for native components

If you have already removed unused apps and cleaned residual code, the next step is to audit the apps you kept rather than reach for another optimizer app. For each one, check the app's settings page for a "lazy load" or "defer scripts" option. Many review apps and chat widgets have this hidden in their config. Turning it on can save another 500ms to 1 second on first paint.

If the bloat is more tangled than your weekend can handle, a help1 expert can walk through your store's script load and clean it in a single 15-minute session. Your first session is free.

How do I prevent shopify page speed from creeping back down?

Once you have a clean theme and a lean app list, the regression hazard is real. Every new app installation is a vote against your speed budget. Build the audit into your routine:

1. Once a quarter, list every installed app and ask the same "actively using in the last 30 days" question. Remove anything that fails it.
2. After every app uninstall, immediately clean the residual code. Do not batch this work; the file-by-file search gets harder when you cannot remember which app left what behind.
3. Before you install a new app, check the Shopify App Store listing for performance disclosure. Apps that publish their script size and defer behavior usually have one because they care about it.
4. Run pagespeed.web.dev on your homepage once a month and log the mobile score. A drop of 5 points or more between months means something new is dragging you down.

If you want this monitoring automated, the help1 store scanner checks your store's app load and theme bloat in under 30 seconds and flags any new render-blocking scripts since your last scan. It also surfaces leftover code from apps you have already uninstalled, which is the part that is hardest to find by hand.

So treat app installs the way a developer treats dependencies. Justify every addition before you click install, clean the residual code the same day you uninstall anything, and re-run pagespeed.web.dev on mobile after each change so you catch a regression while you still remember what caused it. Keep that loop running and your shopify page speed score stays above 70 instead of sliding back down a few milliseconds at a time.