WooCommerce Speed Test
Run Google PageSpeed on your store and see which plugins add the most JavaScript and CSS, plus cart fragments and caching.
Create one in Google Cloud with the PageSpeed Insights API turned on.
What the speed test measures
- 01
Google PageSpeed
Your browser asks Google's PageSpeed Insights API to test the page with Lighthouse, on mobile or desktop. You get the performance score, lab metrics and, where Google has enough visits, real-visitor data from the Chrome UX Report.
- 02
Weight by plugin
Every JavaScript and CSS file from the test is grouped by where it comes from:
/wp-content/plugins/<name>/, your theme, WordPress core, combined cache files or third parties. - 03
Cart fragments
Flags the
wc-cart-fragmentsscript and the?wc-ajax=get_refreshed_fragmentsrequest it can fire on page load. - 04
Caching
Reads the page's response headers (such as
cf-cache-status,x-cache,age) and cache plugin notes to see whether the page came from cache.
Plugin weight is flagged as a warning above 60 KB and as heavy above 150 KB of transferred JavaScript and CSS. Those are this tool's rules of thumb, not Google limits.
The fixes that usually help WooCommerce most
- A page cache. Host-level caching or a cache plugin serves pages without running PHP. Keep cart, checkout and account pages uncached.
- Cart fragments. Since WooCommerce 7.8 the script only loads with the classic cart widget. If it still loads, move to the Mini-Cart block or limit it to shop pages.
- Plugins that load everywhere. Form, slider and page builder plugins often load on every page. Unload them where they aren't used.
- Third-party scripts. Chat, reviews and tracking tags add up. Delay the ones that aren't needed for the first view.
Limits and quota
The PageSpeed API is free but rate-limited when used without a key. If Google's shared quota is busy, the test still reports plugin files, cart fragments and caching from the page itself, and you can add your own free API key from Google Cloud.
Lab scores change from run to run. Compare trends, and trust the real-visitor data for Core Web Vitals when it's shown.
Questions people ask
Why is my mobile score so much lower than desktop?
Lighthouse tests mobile on a simulated mid-range phone with a slower connection, so heavy JavaScript costs far more there.
What are WooCommerce cart fragments?
A script that refreshes the mini-cart with an AJAX request so it stays accurate on cached pages. The request isn't cached, so on busy stores it adds server load and delay.
Why does it say the page wasn't a cache hit?
The first request after a cache clears is a MISS. Run the test again; if it still misses or says BYPASS, the page isn't being cached.
Do I need an API key?
Usually not. Add one only when Google's free shared quota is used up. Create it in Google Cloud and enable the PageSpeed Insights API.
Can I test a Shopify store with it?
The PageSpeed part works on any site, but the plugin breakdown only applies to WordPress.
Related tools
Want this builtinto your store?
I'm Emmanuel, a Shopify and WooCommerce developer. If this tool pointed at something you'd rather have fixed for you (a faster store, cleaner product data, a migration, a custom feature), send me a note.
Emmanuel Asika
Shopify & WooCommerce developer, Dublin
I build and fix online stores: new builds, migrations, speed, SEO and the custom bits apps can't do.
Last reviewed 30 September 2026.
Sources: Google: PageSpeed Insights API, get started · Google: runPagespeed reference · WooCommerce Developer Blog: Best practices for the cart fragments API