How much does a slightly faster website really matter? A study commissioned by Google and carried out by Deloitte and the analytics firm 55 looked at 37 major brand sites and more than 30 million user sessions. Its finding: even a 0.1-second improvement in mobile speed was associated with more people moving through to buy, book or enquire.
Site speed is one of those topics that sounds technical and abstract until it is put in commercial terms. That is exactly what this study set out to do.
What the study measured
According to Google’s write-up on web.dev, the study, called Milliseconds Make Millions, monitored 37 leading European and American brand sites and collected data on more than 30 million user sessions over a 30-day period at the end of 2019. It looked across four types of site: retail, travel, luxury and lead generation.
The researchers examined what happened when four speed metrics — First Meaningful Paint, Estimated Input Latency, Observed Load and Max Server Latency — improved by 0.1 seconds.
What it found
- Retail: conversion rates increased by 8.4%, and consumers spent 9.2% more.
- Travel: booking rates improved by 10%.
- Luxury: a 40.1% increase in users moving from a product page to the add-to-basket page.
- Lead generation: progression to form submission rose 21.6%, and page views increased 7%.
The study’s summary conclusion was that even a 0.1-second improvement in load times can improve progression through the full purchase funnel.
Why speed changes behaviour
Every delay is a chance to leave
Each moment a visitor spends waiting is a moment they might go back to the search results and pick someone else. On a phone, often on a patchy connection, that impulse is stronger.
Speed shapes how trustworthy a site feels
A site that responds instantly feels professional and well run. One that stalls feels neglected, even if the business behind it is excellent. Visitors judge quickly, and slowness colours everything that follows.
Small frictions compound
A customer does not load one page. They load a service page, then a pricing page, then a contact form. A small delay repeated at every step adds up across the whole journey, which is why improvements at each stage move the final result.
What a local business can take from this
The lead generation numbers are the relevant ones
Most local service businesses are, in effect, lead generation sites: success is a phone call or a completed form. That is the category where this study found a 21.6% improvement in progression to form submission. It is a strong reason to treat speed as a sales issue rather than a technical one.
Start with the heaviest things on the page
On most small business sites, the biggest speed problems are oversized images and videos. Photographs uploaded at full camera resolution, background videos far larger than their display size and images saved in heavy formats can add seconds to every visit. Resizing and compressing them is often the quickest meaningful improvement available.
Test on a phone, not your office computer
Your site probably feels fast on a desktop with a good connection. Your customers are more likely to be on a phone in a car park. Check your key pages on mobile, and use a tool such as Google’s PageSpeed Insights to see what is slowing them down.
Protect the path to enquiry
Pay particular attention to the pages closest to a conversion: your service pages and your contact form. A fast homepage followed by a slow contact page loses people at the most expensive moment.
A reality check
This study looked at large brand websites, not small local businesses, and it describes associations observed across many sites rather than a guaranteed result for any one of them. It was also commissioned by Google, which has an interest in a faster web. None of that makes the direction of the finding surprising: faster sites make it easier for people to do what they came to do. Just do not expect a specific percentage uplift from shaving a tenth of a second off your own site.
This article is part of our Media & Insights case study series on marketing lessons from around the world.
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