Shopify Essentials: Why your store is slow, and how to fix it without a rebuild

Most slow Shopify stores are slow for the same few reasons: too many apps, oversized images, heavy theme code, everything loading at once, web fonts and duplicate tracking scripts. You can fix most of them without a rebuild or a new theme.

Here’s each cause, and what to do about it.

1. Too many apps

Shopify apps often load their own scripts, styles and tracking. Some run on every page, even where they do nothing.

The fix

• Uninstall unused apps
• Check which scripts are slow in your browser’s developer tools
• Replace several single-purpose apps with one that covers them, or with a few lines of theme code
• Be wary of “speed booster” apps, which add their own scripts

2. Oversized images

Large, uncompressed images are one of the most common causes of a slow page.

The fix

• Shopify’s CDN resizes images and serves modern formats, but only if the theme asks for sensible sizes
• Upload images close to the largest size they will display at
• Don’t use full-resolution product shots in banners

3. Heavy theme code

Some themes, premium ones included, carry code you don’t use and Liquid that does more work than it needs to.

The fix

• Profile the theme with Shopify’s Theme Inspector for Chrome
• Ask your developer to check for nested loops and unnecessary render calls
• Flatten deeply nested snippets where possible

4. Everything loading at once

If the theme doesn’t control loading, every image and script can load at once, even ones far down the page.

The fix

• Lazy-load images below the fold
• Don’t lazy-load the main banner or first product image, because that delays what visitors see first
• Defer non-critical JavaScript

5. Web fonts

Web fonts such as Google Fonts can hold up the text on the page until they’ve loaded.

The fix

• Preload your font files
• Use font-display: swap
• Use fewer font families and weights

6. Duplicate tracking and third-party scripts

Shopify already serves your theme files and images through its CDN, so caching is rarely the problem. Third-party scripts often are: chat widgets, review widgets, and the same analytics tag added twice, once by an app and once in the theme.

The fix

• Check the theme code, your apps and Shopify’s Customer events settings for tags loading twice
• Load chat and review widgets only on the pages that need them

7. No measurements

Without a baseline, you can’t tell whether a change helped.

The fix

• Test with PageSpeed Insights, GTmetrix or SpeedVitals
• Test the home page and product pages separately

What to do next

1. Test your store in PageSpeed Insights
2. Remove any unused apps
3. Optimise your images and defer non-essential scripts

Related reading

• Shopify theme performance: Liquid optimisation
• Advanced customisation in Shopify themes

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If the store is still slow once the apps and images are dealt with, the theme code is next, and that needs a developer. My guide to hiring a Shopify developer covers what to ask one. Theme speed work is part of my Shopify development service.