Same-store homepage JavaScript change, September to December 2025
| Platform | Stores | Grew more than 10% | Grew more than 25% | Cut more than 10% | Median change | Median bytes added |
|---|---|---|---|---|---|---|
| Shopify | 34,042 | 26.8% | 9.2% | 14.0% | +3.6% | 81.7 KB |
| WooCommerce | 17,349 | 27.5% | 16.1% | 15.3% | +3.3% | 26.5 KB |
| Magento | 7,344 | 22.0% | 10.2% | 12.9% | +2.8% | 39.6 KB |
| All stores | 58,735 | 26.4% | 11.4% | 14.2% | +3.3% | 46.4 KB |
Source: PageSpeed Matters, Dec 2025. Homepage JavaScript bytes only.
Summary
JavaScript is one of the biggest costs on a store homepage, and the holiday season is when many stores make changes. We wanted to know how much homepage JavaScript stores actually add between September and December, and which platforms add the most.
Between September and December 2025, 26.4% of 58,735 online stores grew their homepage JavaScript by more than 10%. The median store grew by a modest 3.3%, from 1.94 MB to 2.01 MB. So most stores stayed close to where they started, while about a quarter added a noticeable amount.
What we measured
We used the HTTP Archive monthly crawls for September and December 2025 and compared each store's homepage with itself. Stores here means Shopify, WooCommerce and Magento sites in the top 1M that ran on the same platform in both months and had Chrome UX Report (CrUX) data. That gave 58,735 stores: 34,042 on Shopify, 17,349 on WooCommerce and 7,344 on Magento.
We measured homepage JavaScript bytes only, not the number of scripts, and not other pages such as product or cart pages.
The data shows timing, not cause. Stores add and remove JavaScript for many reasons, so this study does not attribute the growth to holiday apps or any other specific change.
A quarter of stores added more than 10%
26.4% of the 58,735 stores grew their homepage JavaScript by more than 10% between September and December 2025. 11.4% grew by more than 25%.
The typical store changed far less. The median store grew 3.3%, from 1.94 MB to 2.01 MB of JavaScript, and added 46.4 KB.
Not every store grew. 14.2% cut their homepage JavaScript by more than 10% over the same months. Movement went in both directions, but growth was more common than cuts.
26.4%
Share of 58,735 Shopify, WooCommerce and Magento stores that grew their homepage JavaScript by more than 10% between September and December 2025.
WooCommerce stores bloated most often
By platform, 27.5% of WooCommerce stores, 26.8% of Shopify stores and 22.0% of Magento stores added more than 10% to their homepage JavaScript.
The difference is clearer for heavy growth. 16.1% of the 17,349 WooCommerce stores grew their JavaScript by more than 25%, against 9.2% of 34,042 Shopify stores and 10.2% of 7,344 Magento stores. WooCommerce stores were also the most likely to cut: 15.3% removed more than 10%, against 14.0% on Shopify and 12.9% on Magento. WooCommerce homepages simply changed more, in both directions.
One possible reason is that WooCommerce sites add features through plugins, and each plugin can bring its own scripts to every page. This data does not show that.
Site popularity made little difference. 26.9% of stores in the Top 100K grew by more than 10%, against 26.4% in the rest of the top 1M.
Shopify stores added the most bytes
While WooCommerce stores were most likely to grow heavily, the median Shopify store added the most JavaScript in absolute terms. It added 81.7 KB over the season, against 39.6 KB on Magento and 26.5 KB on WooCommerce.
In percentage terms the medians are close: +3.6% on Shopify, +3.3% on WooCommerce and +2.8% on Magento. A similar percentage change can mean very different byte counts, depending on how much JavaScript a homepage carried to begin with.
An extra 81.7 KB will not break a page on its own. But JavaScript has to be downloaded, parsed and run on the shopper's phone, and small additions each season add up when nothing is removed afterwards.
What this means for your store
If your store is like the quarter that added more than 10% between September and December, the extra weight lands on phones during your busiest weeks. A few habits keep it in check.
- Measure before and after. Record your homepage JavaScript weight in September, then check it again after each new app, plugin or widget you add for the season.
- Load seasonal scripts only where needed. A sale banner or gift widget rarely needs to run on every page.
- Clean up in January. Remove apps, plugins and tags you added for the season once it ends. The 14.2% of stores that cut more than 10% show it can be done.
- Defer what is not needed for the first view. Scripts for chat, reviews or recommendations can usually load after the main content.
- Watch field data. Check your Core Web Vitals in PageSpeed Insights or Search Console, because extra JavaScript often shows up as slower responsiveness on mobile.
Sources
- HTTP Archive monthly crawls, September and December 2025, top 1M sites
- Chrome UX Report (CrUX), used to select stores with field data in both months
- web.dev, Core Web Vitals overview: https://web.dev/articles/vitals
Frequently asked questions
How much JavaScript do stores add over the holidays?
Between September and December 2025, 26.4% of 58,735 stores grew their homepage JavaScript by more than 10%. The median store grew 3.3%, from 1.94 MB to 2.01 MB.
Which platform adds the most JavaScript over the holidays?
WooCommerce stores were most likely to grow heavily: 16.1% added more than 25%, against 9.2% on Shopify and 10.2% on Magento. In bytes, the median Shopify store added the most, at 81.7 KB.
Do stores remove JavaScript after adding it?
Some do. 14.2% of stores cut their homepage JavaScript by more than 10% between September and December 2025, including 15.3% of WooCommerce stores.
Homepage JavaScript is easy to add and easy to forget, which makes a regular script audit one of the simplest speed wins for a store. Need help with this? See our ecommerce CRO agency.