If you’re asking yourself, “Why is my Magento site so slow?”, you’re in the right place. Many Magento store owners face frustratingly slow load times, and the cause isn’t always obvious. You may have fast hosting, a decent theme, and even caching enabled — yet the store still drags.
Below are 7 hidden performance killers that often go unnoticed but can dramatically slow down your Magento site. Fixing just a few of these can shave seconds off your load time and boost conversions immediately.
1. Uncached Blocks in Layout XML
Magento uses layout XML to determine which blocks are cacheable. If these are misconfigured or missing cacheable="true", your pages will bypass Full Page Cache and render dynamically on every request.
How to fix it:
- Audit your custom modules and themes for dynamic blocks
- Use layout XML to explicitly mark blocks as cacheable
- Use
varnishlogor debug headers to confirm cache hits
2. Flat Catalog & Indexing Settings
Outdated indexing settings or enabling Flat Catalog in Magento 2 (which is deprecated) can cause performance degradation.
How to fix it:
- Disable Flat Catalog (Stores > Config > Catalog > Storefront)
- Set indexing to “Update on Schedule”
- Reindex via CLI regularly:
bin/magento indexer:reindex
3. Poorly Optimized Product Images
Magento doesn’t optimize images by default. Many merchants upload 2MB+ images that load above-the-fold, crushing LCP scores.
How to fix it:
- Convert all images to WebP
- Use responsive image sizes (especially on PDP and category pages)
- Preload LCP images and fonts
4. Unused or Bloated Extensions
Magento is often bloated with extensions that add overhead — even when disabled. Some still load observers or UI components.
How to fix it:
- Run
bin/magento module:statusand remove anything unnecessary - Profile the site with
n98-magerun2orBlackfire - Avoid frontend-heavy extensions like page builders and chat widgets
5. Broken JS & RequireJS Overhead
Magento’s RequireJS can lead to dozens of blocking JS requests. Even one broken dependency can delay page rendering.
How to fix it:
- Disable built-in bundling, switch to custom bundling (Webpack/Rollup)
- Check for JS errors in dev tools
- Consider migrating to Hyvä if feasible
6. Theme Loading External Fonts Without Preload
Fonts from Google or Adobe that aren’t preloaded can delay First Contentful Paint (FCP).
How to fix it:
- Host fonts locally
- Add preload directives in your
head.phtml - Use
font-display: swapfor faster fallback
7. Admin & Frontend Competing for Resources
Running admin-heavy tasks (importing, indexing) during traffic hours can hurt frontend performance.
How to fix it:
- Schedule backend tasks during low-traffic times
- Use separate admin and frontend servers if possible
- Monitor resource usage during imports
Get the Fix: Join the Free 7-Day Magento Speed Challenge
Each day you’ll receive one simple action you can take to speed up your Magento store. Sign up here: 7-Day Challenge
Need a Complete Guide? Download the Magento Optimization Checklist
This checklist includes 370+ performance improvements to help you fix, test, and optimize every aspect of your store. Download it here: Magento Optimization Checklist