Adding apps to a store is a common way to enhance and expand your customer's experience. Apps often require theme file changes to properly connect, but these modifications can remain in place even if the app is removed from the dashboard. Page speed delays, theme errors, and other problems can come from leftover app code changes. Refer to this guide for actionable steps to remove them.
Contact the app developers
No one knows how and where an app integrates with the theme files better than the app's developers. Their team would be most equipped to help you in removing their app's code.
App developers can be contacted through the App Store.
Compare theme files to the default theme
A clear way to find the files or file changes to remove would be to compare individual theme files to their default state. It is still ideal to reach out to the app's developers for this, as well. There are numerous theme files and comparing them manually could be a tiresome task without guidance.
Get the default copy for comparison
Use the Theme Updater for installing a default copy of the latest theme version.
Compare to your theme files
Use a tool like Diff Checker to compare your theme files. Theme files can be accessed by going to Actions > Edit code in your Online Store's Themes.
Start fresh with the latest theme version
Sometimes it's more achievable to take the latest release of a theme and build up from there. Starting with the default theme, then installing only the necessary apps would be the ideal starting point for minimal 3rd-party files or scripts.
To complete this task, add a blank copy of the latest version to your store:
Then contact the app developers of the apps you need to keep. They can confirm the installation steps needed for the new version. Once this is complete, add your content and adjust your settings to match your previous storefront.