Why your Shopify speed score drops after every app install, and the 20 minute fix.

What actually happens when you install an app

Most Shopify apps need to run code on your storefront. The clean way is a theme app extension, which loads through {{ content_for_header }} and switches off the moment you uninstall. The older way, and still a common one, is the app writing a <script> tag straight into theme.liquid or a snippet, then relying on you to remove it later.

Nobody removes it later. We open theme files every week that still load review widgets, popup tools and pixel managers for apps the store stopped paying for two years ago. Each one is a network request, a parse, and often a second request the first one triggers. Ten of them on a product page is a measurable second on a mid-range phone, and a direct hit on INP, the Core Web Vital most Shopify stores fail in 2026.

The speed score dropping after an install is the visible symptom. The invisible one is that the score never comes back after the uninstall, so each app cycle leaves the store a little heavier than before.

Finding the leftovers in ten minutes

Duplicate your live theme first so nothing you do here touches customers. Then, in the duplicated theme:

1. Open Edit code and search the whole theme (the search box at the top of the file list) for <script src=. You will get a list of every external script the theme loads.

2. For each domain you do not recognise, check it against your installed apps list. If the app is gone, the line goes.

3. Repeat the search for cdn.shopify.com/s/files plus .js. This catches scripts apps uploaded as theme assets.

4. Check Settings, then Customer events in the admin. Custom pixels live there and are easy to forget.

5. Open Online Store, Themes, Customize, App embeds. Toggle off any embed for an app you no longer use. These are cleaner than theme edits but still load if left on.

Write down what you removed. When the theme is published, that list is your rollback plan if something on the page looks wrong.