Website slower after a redesign? Why it happens and the fix

Key takeaways

A website is often slower after a redesign because the new design asked for more than the old one: larger images, more fonts, animation, a heavier theme and extra tools. The old site's caching and image settings may also not have been carried across. It is usually recoverable without undoing the design. Confirm the slowdown with data, find the heaviest additions and fix them in order.

• New designs add weight: bigger images, more fonts, motion and features.
• Caching and image optimisation are often lost in the move.
• Compare the same pages on mobile, before and after.
• Most of the loss can be recovered without changing how the site looks.

Why are redesigned sites often slower?

Redesigned sites are often slower because a redesign is judged on appearance. The design is approved on a large monitor, the build is checked on office broadband, and nobody is asked to keep the new site as fast as the old one.

Each element of a modern look has a cost. A full-width photograph, a custom typeface in several weights, scroll effects, a video header and a new set of plugins all add weight the previous site did not carry.

• How website speed affects customer experience and conversions
• Website speed vs design: do you have to choose?

How do you confirm it is slower?

Confirm it with the same measurements on the same page types. If a baseline was recorded before the redesign, compare against it. If not, Search Console's Core Web Vitals report keeps a history that shows whether pages moved from good to needs improvement after the launch date.

• Compare field data before and after launch, allowing 28 days.
• Compare mobile engagement and enquiry rate for the same landing pages.
• Test the new templates on a mid-range phone over mobile data.
• Check server response time on several pages.

• How to test website speed the way customers feel it
• Measure your website before a redesign

What are the usual causes?

The causes are consistent enough to check in order.

• Images migrated or uploaded at full size, with no automatic resizing.
• Page caching not switched on in the new setup.
• A heavier theme or page builder than the old site used.
• More fonts, in more weights, from an external service.
• Animation, sliders or video added to the first screen.
• Old tracking tags kept and new ones added alongside.
• New hosting that is slower than the old.

• Website caching explained for business owners
• Optimise website images for speed and search
• Website animations: when motion makes a site feel slow

How do you recover the speed?

Start with what was lost in the move, then deal with what was added.

• 1. Turn on page and browser caching.
• 2. Resize and convert images, and set up automatic handling for new uploads.
• 3. Remove duplicate and unused tags.
• 4. Cut fonts to the weights in use and host them on the site.
• 5. Replace first-screen video and sliders on mobile.
• 6. Switch off entrance animations.
• 7. Re-test, then review the theme only if the site still fails.

• Third-party scripts: the hidden reason your site is slow
• Slow website: fix it or rebuild it?

Whose job is it to fix?

It depends on what was agreed. If the contract set speed requirements, failures within the supplier's scope are theirs to correct. If it did not, the conversation is harder, but a reasonable supplier will fix omissions such as caching and image handling, which are part of building a site properly.

Raise it promptly and with evidence: the pages, the mobile results and the date they changed. A redesign that also lost search traffic needs a separate check of redirects and content.

• Speed requirements to put in a website contract
• Traffic dropped after a website redesign? Recovery steps

What does this look like in practice?

A pattern we see a few months after launch: the new site looks far better and mobile enquiries have slipped. The old site, for all its faults, was light. The new one opens with a video, loads eight font files and was moved to new hosting without caching.

Restoring caching, serving a still on mobile and trimming the fonts keeps the new look and returns the speed. Across client work at Global Bridge Labs (GBL), we have seen a 2.4x enquiry rate from conversion changes like these.

• See client work
• Website Design & Development for UK businesses

Post-redesign speed checklist

• Compare Core Web Vitals before and after the launch date.
• Check caching is on.
• Check image sizes on the new templates.
• Count fonts, tags and plugins against the old site.
• Test the first screen on a phone.
• Raise failures with the supplier, with evidence.

• The website speed scorecard: score your site in an hour
• Website redesign mistakes that cost enquiries

Next step

A redesign should not cost you the speed you had. We will compare the new site with the old and give you a list of what to recover and in what order.