Website Speed & SEO
What a tenth of a second is worth to an online store
Google and Deloitte measured what happens when mobile sites get 0.1 seconds faster. Here is what the data says, what usually slows a store down, and how to fix it without a rebuild.
Most brands treat site speed as a technical chore. The data says it is a revenue line.
What the research found
In late 2019, Deloitte and the agency 55 ran a study commissioned by Google. They tracked the mobile sites of 37 major European and American brands for 30 days, across more than 30 million user sessions, and compared how shoppers behaved as load times changed. To count, a site had to get 0.1 seconds faster on every page of the journey.1
The results for a tenth of a second:
- Retail: conversion rates rose 8.4%, and shoppers spent 9.2% more. The step from product page to add-to-basket alone improved 9.1%.1
- Travel: conversion rates rose 10.1%.1
- Lead generation: progression to the form submission page rose 21.6%.1
Earlier Google research points the same way from the other side. As mobile load time goes from one second to seven seconds, the probability that a visitor bounces rises 113%.2 In the same body of research, sessions that bounced loaded about 2.5 seconds slower on average than sessions that did not.3
Speed also matters for search. Google evaluates page experience, including Core Web Vitals, as part of how it ranks pages, alongside content relevance.4 A faster site does not replace good content, but a slow one makes good content harder to find.
Why stores get slow
In most cases, the cause is rarely the platform itself. It is what has been added on top of it over the years:
- Apps and tracking scripts that load on every page, including ones nobody uses anymore.
- Images uploaded at full camera resolution and served to phones without resizing or modern formats.
- Themes built for looks first, with sliders, video backgrounds and fonts that block the page from appearing.
- Third-party widgets for reviews, chat and popups that each add their own requests.
None of these is fatal on its own. Together, they turn a two-second page into a six-second one.
How to fix it without a rebuild
- Measure the pages that make money. Start with your homepage, top collection pages and best-selling product pages on a phone. Our free site check runs Google's own test on any page.
- Remove before you optimize. Audit every app and script. Anything that does not earn its weight goes.
- Fix images at the source. Resize, compress and serve modern formats automatically, so new uploads stay fast without anyone remembering to do it.
- Load what is visible first. Defer reviews, chat and below-the-fold content until the main content is on screen.
- Watch it continuously. Speed regresses every time someone installs an app. Automated monitoring catches it the same week instead of the next quarter.
Where AI fits
Speed work is mostly engineering, but AI removes the slow parts around it. We use AI to generate optimized titles, descriptions, alt text and structured data across thousands of products, so the speed gains come with better search listings too. We also set up automated checks that alert you when a page gets slower or a key SEO field goes missing.
The takeaway
A tenth of a second sounds trivial. Across a year of traffic, it is not. If you want to see where your site stands, run the free check, then request a consultation for a full audit with a prioritized fix list.