Wix, Squarespace and Webflow: what you can speed up

What a hosted builder gives and takes

A hosted builder runs your site on its own servers, with its own caching and its own code. You use a visual editor and choose a template. You do not pick the host, install a cache or edit the theme's files the way you would on WordPress.

The 2025 Web Almanac puts the trade-off this way. Platforms that limit customization tend to reduce risk through consistent defaults. Extensible systems such as WordPress shift more responsibility onto site owners and implementers, and their results spread wider. So a builder gives you a decent floor and less room to go above it.

We have not tested the settings screens of each builder here. The advice below comes from how pages are built and from the Almanac's data, so check the details in your builder's help pages.

What the 2025 data shows

These figures come from the Web Almanac's CMS chapter. They are medians and shares across all the sites it detected on each platform, and they say nothing about your site. All the Core Web Vitals figures are for mobile.

• Wix. 74% of Wix sites passed all three Core Web Vitals, up from 55% a year earlier. 81% had a good Largest Contentful Paint and 95% good layout stability. The median Lighthouse performance score was 64 on mobile and 87 on desktop. The chapter names Wix as the platform that gained the most in a year, about 14%.
• Squarespace. 96% of sites had a good Interaction to Next Paint, the best figure in the chapter, and 89% had good layout stability. Its median page was the heaviest of the five platforms compared, at 3,974 KB.
• Webflow. The median Lighthouse performance score was 58 on mobile and 73 on desktop.
• For comparison. 45% of WordPress sites passed all three, 53% had a good Largest Contentful Paint and about 84% good layout stability. The Lighthouse medians were 41 on mobile and 63 on desktop. Duda was the best performer, with 85% of its mobile sites passing.

The chapter also says that no platform delivers excellent interaction speed consistently at scale.

The weight profiles differ

The chapter compares what mobile pages are made of for five platforms: Joomla, Squarespace, WordPress, Wix and Shopify. The medians for the three builders and WordPress:

• Wix. The smallest image weight, at 194 KB, and the largest HTML, at 162 KB. The most JavaScript besides Shopify, at 1,634 KB. Almost no CSS from separate files, about 1 KB.
• Squarespace. The heaviest pages in total (3,974 KB), among the highest image weights, and the most CSS, at 165 KB. HTML among the smallest.
• WordPress. 2,894 KB in total, 638 KB of JavaScript and 119 KB of CSS.

The pattern is clear even without every number. Wix pages carry little image weight and a large amount of JavaScript. Squarespace pages are heavy in images and CSS. The Almanac adds that heavier pages are more likely to miss the Core Web Vitals thresholds, especially on mobile, and that two sites on the same platform can still differ widely.

What you control

Because the platform fixes the base, you work on what you add:

• Images. Images are the biggest part of page weight on every platform in the data. Upload photos at the size you need, not at the size the camera gave you. Use fewer images per page, and keep the main one modest. See image optimization. Check whether your builder resizes and converts what you upload, and make sure the main image is not set to load late.
• Fonts. Each font family and weight is a file. Use one or two families and few weights. See web fonts.
• Effects. Scroll animations, parallax, hover effects, sliders and background video all add scripts. Use them where they earn their place, and not on the first screen.
• Apps, widgets and embeds. Chat, booking, reviews, social feeds, maps, video embeds and pop-ups are other companies' code. They add the most weight that you control. See third-party scripts.
• Tracking code. Every pixel and analytics tag you paste into the site's header runs on every page. Keep the ones that someone uses.
• Page structure. A page with many sections, each with its own images and effects, is heavy. Split long pages, or cut the sections that do not help a visitor decide.
• Mobile design. Test the phone view. Content that is hidden on a phone can still be loaded.

What you usually cannot change

On a hosted builder you generally cannot set caching headers, choose a server location, install a cache plugin, edit the platform's own scripts or turn off parts of its base code. Your builder's settings may offer some of these in limited form, and its help pages will say which. If the platform's base weight is the main cost, content changes will only take you so far.

How to test a builder site

1. Test several pages, not only the home page: a service or product page, a blog post and a contact page. Use a phone profile.
2. Take the median of several runs. Scores move between runs. See why scores change.
3. Look at real-visitor data if your site has enough traffic. See the Chrome UX Report. It is the data that counts for Google's Core Web Vitals.
4. Check any score in your builder's dashboard against PageSpeed Insights. Different tools measure differently, and you want the one your visitors and Google see.
5. Change one thing at a time, then test again. A builder can update its own code without notice, so a score may move when you have changed nothing.

When to move off a builder

Moving takes time and carries risks to your search visibility, so do it for a clear reason. The reasons that can justify it:

• After trimming images, fonts, effects, apps and tracking, your key pages still miss the thresholds, and the real-visitor data confirms it.
• You need control that the platform does not offer, such as server-level caching, a different host or direct access to the code.
• Your pages need features that a hosted builder cannot give without heavy add-ons.

Before moving, check how far a better-built template or a leaner design can take you on the same platform. If you move, plan the new address structure, set up redirects from every old address, and test a copy first. Compare the numbers before and after, with the same pages and the same method.

Mistakes to avoid

• Judging by the template's demo. Demos are built with the template's best images and no apps.
• Stacking effects and apps. Each is small. Together they decide the result.
• Uploading camera originals. They cost weight on every visit.
• Trusting a dashboard score alone. Check it against the tools above.
• Moving too early. Trim what you control first. Most of the gain is often there.

Check your own page

Run the free audit on your home page and on a page with a lot of content. Open the list of the largest files and 3rd parties. If the biggest items are your own images, replace them. If they are apps and embeds, decide which you can drop. If they belong to the platform and you cannot touch them, that tells you how much room you have.

Sources

• CMS chapter, Web Almanac 2025: the Core Web Vitals pass rates by platform, the Lighthouse medians, the page weight by type, and the comparison of controlled and extensible platforms.
• Ecommerce chapter, Web Almanac 2025: the platform types and the ecommerce results for Wix and Squarespace stores.