Why Optimise Website Speed?

Website speed matters. Not just because Google says so.

The human mind perceives an interface's immediate response within a mere few hundred milliseconds. Most websites today struggle to meet this threshold during loading, but every improvement counts.

Speeding up your website is likely to boost conversions, as countless case studies suggest. This is why Google supports fast websites, and as a result, speed can also help with traffic and even ad costs.

Google supports fast websites because speed impacts conversions. And also because the human mind doesn't possess infinite patience.

Let us first explore the crux of the matter, which lies in the psychology of human patience when interacting with user interfaces.

Psychology#

When R. B. Miller conducted his early tests in 1968 to understand how users of mainframe computers perceived terminal interface response times, he probably didn't envision that his study would remain highly cited over fifty years later.

Among other insights, he discovered that the magical boundary at which an interface's response is perceived as instantaneous is around 100 milliseconds.

Mr. Miller would likely be rather surprised that, even by 2020, we still can't load and render websites quickly enough to prevent users from waiting anxiously. Sadly, as users, we all know that reaching those hundreds of milliseconds is quite a stretch.

Technology has leapt forward from mainframe terminals to modern web on smartphones, yet human psychology remains unchanged.

From the way our minds are wired, it's clear that if you speed up a user interface, it will better achieve its goals.

Impact on Conversions#

The link between website speed and conversion rates stems not only from Miller's findings and others but also from practical case studies that have been proliferating over the last decade.

All studies show that improving speed positively impacts the business or goals of the website owner.

Bounce Rate#

“Bounce rate” is one of the most closely monitored general analytics metrics. It is assumed from numbers and graphs that speeding up the initial render of a website also improves the bounce rate.

Correlation between speed and bounce rate using a website example (Source: SpeedCurve)

For examples of speed's impact on bounce rate, let's look globally:

• 53% of visits are likely to be abandoned if a page takes more than 3 seconds to load. One of the most notable case studies comes from 2016 by DoubleClick, now part of Google. (Source)
• Radins.com improved the speed of first-screen rendering on desktops, reducing the bounce rate by 25%. (Source)

Pageviews#

In some sectors, especially those driven by advertising, the number of pageviews determines business success or failure.

“At BBC, we noticed that for every second of delay in page loading, 10% of users leave. If BBC's site slows due to loading, certain features are automatically disabled to speed it up again.”

— Matthew Clark, lead technical architect at BBC

What case studies do we know about speed's influence on “pageviews”?

• Shopzilla reduced page load time by five seconds and achieved a 12% better conversion rate and a 25% increase in pageviews.
• The Financial Times added a one-second delay to each page view and recorded a 4.9% drop in pageviews. A three-second delay led to a 7.2% drop. (Source)

Conversion Rate#

When speed improves, the conversion rate follows suit. If you run an e-commerce site, this will interest you. It is usually challenging to isolate the effect of speed optimisation from other factors for our clients, but once we got lucky.

Czech price comparison site Srovname.cz benefited from our Martin Michálek speeding up their site, increasing mobile conversion rates by 25% - Source

• Deloitte Digital showed conversion growth across 37 brands' websites with just a 100 ms speed-up. (Source)
• Walmart calculated back in 2012 that speeding up homepage load time by one second increased their website conversions by 2%. (Source)

There are many case studies worldwide, nicely gathered on the website wpostats.com.

As these figures demonstrate, speed affects a range of critical metrics. This is why Google's team decided to focus on this easily measurable factor of user experience.

The Google Argument#

Occasionally, we encounter conversations like this:

— “Why are you planning to address speed?”

— “Google wants us to”

This might suggest that the entire field of website speed is based on the outcome of a few internal corporate meetings at Googleplex. We imagine these meetings attended by several managers, engineers, and a large crystal ball.

Are Google's recommendations on website speed built on shaky ground? Nothing could be further from the truth.

The world's largest search engine employs outstanding experts in speed technology and researchers backed by data. A recent example is the article The Science Behind Web Vitals, which shows the data behind the new metrics recommendations.

Google simply relies on data, which increasingly shows the connection between a good user experience and the speed of loading and interacting with websites.

Web Vitals and Page Experience Signal#

In a recent blog post Evaluating page experience for a better web, Google announced that they are working on a new ranking signal, “Page Experience”, where speed will play a significant role.

Google will focus on security, user experience, and speed in the "Page Experience" signal.

This isn't the first time the search engine has announced an emphasis on speed. But it is the first time they've plainly stated how they will measure speed. They will focus on Web Vitals metrics, gathered directly from Chrome users and stored in the Chrome UX Report.

The most important speed metrics for every website – Core Web Vitals.

Google will roll out the new signal in 2021, so it wouldn't hurt to prepare.

We've already focused on Web Vitals with our clients. Let's look at the individual metrics and supplement them with some of our successful optimisations.

Core Web Vitals optimisation on Shoptet sped up the deNatura.cz shop and brought in +17% traffic from Google.

LCP (Largest Contentful Paint):

We helped ČistéDřevo.cz e-shop identify backend issues, significantly improving the LCP metric.

INP (Interaction to Next Paint):

We assisted Sazka in identifying JavaScript performance issues caused by code in Google Tag Manager, negatively impacting the INP metric.

CLS (Cumulative Layout Shift):

During our collaboration with Pet Hardware, our expert Michal Matuška identified and resolved issues with unwanted layout shifts during rendering.

Google Ads and Mobile Speed Score#

If you invest in Google-run advertising, you're likely familiar with Mobile Speed Score, which Google uses to rate your campaign's landing pages.

Speed score impacts the cost and position of your ads, so it's worth focusing on it a little.

During one phase of our collaboration with our largest client, Livesport.cz, which offers fast sports results service, our advice helped their excellent team significantly improve the first contentful paint (FCP) over six months: FCP metric development for Livesport.cz users up to February 2020.

The subsequent improvement in Speed Score in Google Ads was more than satisfying:

	August 2018	January 2019
Europe	4-7	9-10
Japan	1-2	10
Africa	1-2	6-7
Australia	1	7-9
Brazil	1-2	7

Impact on Search Engine Rankings#

Before Google implements the Page Experience signal, the direct influence of website speed on SEO remains a topic of debate.

Speed cannot be easily isolated from other signals, and a study on the correlation of speed with search rankings would need to compare practically identical websites. If we find such sites, we'll let you know.

Curious about our opinion? All of Google's communications make it clear that they regard speed as an important signal. So, being significantly slower than your competition is not advisable.

If we set aside psychological and business reasons for speed and focus on SEO, the community agrees on one thing – having a fast server is beneficial.

Correlation of TTFB (Time To First Byte) with Google rankings. - Source

TTFB metric, or the simplified speed of your server and infrastructure, is crucial not only for overall website speed but likely for search ranking positions and “crawl budget”, the number of pages Google can process from your site.

Our recommendation to focus on the backend for this globally operating client significantly improved metrics.

Server speed, as well as client-side code, naturally also affect another factor considered by search engines – Dwell Time, the time between a click from search results to your page and returning back.

Backend optimisation is thus a key discipline.

How to Start Improving Website Speed?#

There are many places to start. The process is always the same, however. The most important thing is to determine where you stand, track progress over time in various contexts, and find the right opportunities for improvement:

1. Measure your speed, ideally alongside your direct competition in our website speed tester.
2. Regularly monitor your website's speed using monitoring.
3. The tester will measure the speed of tested websites daily, so save your test URLs or sign up, and we'll send you a monthly report on the status.

If you see room for improvement in speed, order a website speed audit that includes tailored advice for your project. Or simply reach out – info@pagespeed.cz.

Data Over Promises#

On Srovname.cz, mobile conversions increased by 25%. How we achieved this, and the specific modifications that led to this, can be read in the case study.