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Improving website performance is like regular exercise:
Everyone says it’s important, but few people actually do it.
Here’s why:
Optimizing performance/site speed is hard. And to be perfectly honest - it’s not all that exciting.
That’s why it’s essential to know why we should go through the trouble of doing it.
Put simply, web performance matters to business goals, like brand loyalty, sales and revenue.
But don’t take my word for it.
Below you can find 22 case studies that show speed’s direct effect on business results.
These studies were conducted by some of the most successful online businesses, including Amazon, Google and Netflix.
Let’s dive in.
Year: 2009
Industry: eCommerce
Affected Metrics: Conversions
Context: Back in 2009, few people cared about web performance. But then the biggest eCommerce website in the world said that site speed directly affects their sales. While the original case study is hard to find, Amazon has been used as an example of why speed matters ever since.
Key Finding: Every 100ms of latency cost Amazon 1% of their sales.
Year: 2009
Industry: Internet
Affected Metrics: Searches per user
Context: The next giant that started talking about speed was Google. In 2009 they also had an “intuition” that speed matters a lot. And data showed that they were right. Since then, no one has done more to advance web performance standards than Google.
Key Finding: The cost of bad performance increases and persists over time.
Year: 2009
Industry: Video sharing
Affected Metrics: Traffic and user engagement
Context: As a Google company, it’s logical that YouTube also started investing in web performance around 2009. Their team dug deep into the speed problem and saw that entire continents couldn’t use their service. This realization eventually led to the creation of imgix.
Key Finding: People experience different latencies, depending on their device and network connections.
Year: 2010
Industry: Internet
Affected Metrics: Conversions
Context: In 2010, the browser war was firmly underway. That’s when Firefox tried to replicate Google’s web performance findings. Firefox’s results surprised even their own team, as site speed affected conversions much more than anticipated.
Key Finding: Reducing the average page load time by 2.2 seconds increased download conversions by 15.4%.
Year: 2012
Industry: eCommerce
Affected Metrics: Conversions, bounce rate and revenue
Context: Three years after Amazon announced its focus on speed, Walmart published this detailed presentation of their web performance. It’s clear that by 2012, Walmart already had a sophisticated web performance team. Earlier that year, around 2,2% of the Global Internet usage had gone through their website on Thanksgiving alone.
Key Finding: Speeding up pages by 100ms affects incremental revenue by up to 1%.
Year: 2014
Industry: eCommerce
Affected Metrics: Conversions and bounce rate
Context: Staples knows how important user experience is. Naturally, site speed became their focus after they saw how much it affected giants like Amazon, Yahoo and Walmart. Their case study starts with a very simple but important message: “Performance is a Business Problem”.
Key Finding: Refactoring CSS and JavaScript code reduced homepage load time by 1s, improving conversions by roughly 10%.
Year: 2015
Industry: Media
Affected Metrics: Pageviews and returning users
Context: 2015 was a rough time for mobile web performance. That’s when Google (AMP) and Facebook (Instant Articles) both tried to address speed problems on mobile news sites. As an A/B testing company, Optimizely decided to delay The Telegraph on purpose to test just how much pageviews decreased.
Key Findings: An 8-second load time delay results in 17.52% fewer pageviews
Year: 2016
Industry: Media
Affected Metrics: Article views and revenue
Context: As a media company, the Financial Times (FT) was also affected by the shift to mobile devices. And they knew they had to improve their website’s performance to stay relevant. That’s why they set out to see how much speed affected their core business metrics.
Key Finding: 1-second delay in page speed leads to a 4.6% drop in article views.
Year: 2016
Industry: eCommerce
Affected Metrics: Conversions and revenue
Context: Mobify works with many online retailers, so it's no surprise that they have lots of web performance data. Their 2016 report focuses on the impact that speed has on homepages and checkouts. It also shows the direct effect of web performance in dollars.
Key Finding: For every 100ms of improved checkout load speed, Mobify’s customers saw 1.55% more conversions on average.
Year: 2017
Industry: eCommerce
Affected Metric: Conversions and revenue
Context: Zitmaxx Wonen is an online store that found itself in a very typical situation back in 2017. Mobile traffic was skyrocketing, but their website wasn’t optimized for mobile. This case study details the project they took on to measure, analyze and improve their performance.
Key Finding: Getting a perfect 100 on Google’s PageSpeed Insights and reducing the website’s load time under 4 seconds led to mobile conversions increasing by 50.2%.
Year: 2017
Industry: Internet
Affected Metrics: Conversions and bounce rate
Context: By 2017, Google had more than enough data about site speed’s impact. They also knew that people demanded faster mobile websites. In this analysis, they computed how much bounce rate probably increases as page load time worsens.
Key Finding: As load times go from 1s to 3s, the probability of bounce increases by 32%.
Year: 2018
Industry: Tech & Entertainment
Affected Metrics: Time to Interactive and user clicks
Context: At this point, Netflix has become synonymous with tech excellence. Their infrastructure is beyond impressive and they constantly share their approach to microservices and DevOps. That’s why it’s no surprise that they also spend tons of time and effort on web performance.
Key Finding: Prefetching HTML, CSS and JavaScript reduces Time to Interactive by 50%.
Year: 2018
Industry: Media
Affected Metrics: Bounce rate
Context: BBC is one of (if not the) biggest traditional news publishers online. According to Similarweb, BBC's main site alone generates over 1.5 billion page views per month. Optimizing a website for that type of traffic is a problem that I hope we also have at some point.
Key Finding: BBC’s website loses 10% of its visitors for every additional second of load time.
Year: 2018
Industry: Internet, technology, lodging and eCommerce
Affected Metrics: Conversions, user engagement, Speed Index, Time to Interactive and others
Context: This is a big success story compilation by Google. It’s a practical look at ten businesses (including Walmart, Airbnb and eBay) with their reasons and approaches to improving site speed.
Key Finding: It is hard to pick just one finding since this is a collection of case studies. But an important theme that runs through the entire talk is this: Everyone in your organization must understand that web performance is a vital factor for success.
Year: 2018
Industry: eCommerce
Affected Metrics: Conversions, bounce rate and mobile traffic
Context: I’ve talked about why image optimization is often the best thing you can do for site speed. This case study perfectly illustrates my point. Using ImageEngine, Furnspace saw impressive site speed and revenue results only by optimizing their images.
Key Finding: Image optimization decreased load time by 65%, leading to a 2x increase in conversions.
Year: 2019
Industry: Internet
Affected Metrics: Abandonment rate
Context: Back in 2018, Google announced that page speed would become a ranking factor for mobile searches. The SEO world went crazy. Everyone scrambled to fix their broken mobile websites, which they should’ve done years ago. This article summarizes the results from this experiment a year later.
Key Finding: With speed improvements across the globe, Google saw a 20% reduction in abandonment rate for navigations initiated from search.
Year: 2020
Industry: Internet
Affected Metrics: Abandonment rate
Context: The addition of the Core Web Vitals was Google’s biggest contribution to web performance in 2020. In this article, they explain how these three metrics affected vital performance indicators during their research.
Key Finding: Websites that met the thresholds for all three Core Web Vitals saw up to 24% less abandonment rate.
Year: 2020
Industry: Media
Affected Metrics: User engagement, revenue, bounce rate, and Largest Contentful Paint (LCP)
Context: This is one of the first comprehensive case studies about LCP’s effect on user engagement. As a news station, NDTV needs its largest above the fold elements to load quickly (like Yahoo and Google News). That’s why improving their LCP and CLS had such a massive impact on bounce rates.
Key Finding: 55% improvement in LCP time led to bounce rate decreasing by 50%.
Year: 2020
Industry: eCommerce
Affected Metrics: Click-through rate (CTR), conversion rate, and Time to Interactive (TTI)
Context: As one of the largest eCommerce companies in Indonesia, with 50M+ monthly visitors, the team at Tokopedia is constantly investing in tools and features to improve their web performance. Their latest experiment was to create a web performance dashboard and optimize JavaScript, resources, and the homepage to see how that will affect business results.
Key Finding: By implementing various JavaScript and image optimizations, they achieved a 35% increase in CTR, 8% increase in conversions, and reduced their app’s JavaScript script size by 88%.
Year: 2021
Industry: Telecommunications
Affected Metrics: Largest Contentful Paint (LCP), sales, lead to visit rate, and cart to visit rate
Context: Vodafone is a telecommunications giant that knows that faster websites generally correlate to improved business metrics. Looking for a new sales improvement strategy, they decided to optimize their site’s Web Vitals and see whether that would give them the boost in conversions they were after.
Key Finding: A 31% improvement in LCP led to 8% more sales, a 15% improvement in their lead to visit rate, and an 11% improvement in their cart to visit rate.
Year: 2021
Industry: eCommerce
Affected Metrics: Core Web Vitals, page load time, revenue, and relative mobile conversion rate (Rel mCvR)
Context: Swappie is a successful start-up that sells refurbished phones and for a few years they prioritized adding new features over site performance. However, when they noticed that their mobile revenue started falling behind the desktop version of their website, they decided that it was time for a change. To attack the issue they decided to focus on improving Core Web Vitals which yield the results they were looking for.
Key Finding: Improving their Core Web Vitals led to a 23% lower average page load time, and a 42% increase in revenue coming from mobile visitors.
Year: 2021
Industry: Automotive
Affected Metrics: LCP, conversion rates, and bounce rates
Context: After analyzing data from 10 million visits on its landing pages, Groupe Renault’s team found a strong correlation between Largest Contentful Paint and conversion rate. Their goal - optimizing the website until the LCP reaches below 1 second.
Key Finding: 1 second LCP improvement can lead to a 14 percentage points (ppt) decrease in bounce rate and a 13% increase in conversions.
To sum up, I believe this quote from Mobify’s report (#9) encapsulates this article perfectly:
Faster Websites = Deeper Engagement = Higher Conversion
It’s. That. Simple.
This has been proven over and over again by some of the most successful businesses ever. Additionally, financial planning and analysis are crucial to ensure they make sound investments in their website's performance, as it can directly impact their bottom line.
In short, if you want to compete online, you need to fix your website’s performance. Consider flipping through the best site speed optimization tools for 2023.
To get started on the path to a faster website, open these for further reading:
Evgeni writes about site speed and makes sure everything we publish is awesome.
