This article was originally published by Stéphane Rios.
While it seems vital for e-merchants to display their pages in less than three to five seconds, including on cell phones, it is important to optimize their frontend and to be part of their ecosystem.
Good loading speeds are essential for the user experience. Indeed, the faster the loading process, the more Internet users are able to stay on a website, visit a large number of pages, and finalize their purchases, instead of leaving it out of frustration. Beyond the ease of browsing, speed is also an issue for turnover and SEO. This is the reason why it is necessary to know how to evaluate it, but also to compare oneself to one's own ecosystem in order to draw the necessary conclusions.
A fast website for a better user experience
With fast website pages, users' attention is held. They are driven in a "flow", their focus and commitment are at their peak. In terms of perception, a Google study reveals that for the display of pages:
< 200 milliseconds give an impression of immediacy
< 1 second gives an impression of fluidity
< 5 seconds is acceptable to maintain the "flow".
< 8 seconds result in loss of attention.
In an environment where there are multiple demands and where our attention span is decreasing, display speed is essential. In fact, it is the number one UX requirement for mobile users, ahead of the aesthetic aspects of an interface. It only takes three seconds to wait for 53% of mobile users to leave a page if it is not loaded. Once they leave, these visitors will not come back, and there is even a good chance that they will go to a competitor's website.
Therefore, the speed of the website pages counts at each step of the shopping chain, until the validation of the shopping cart. A 2018 ComScore study found that 20% of shopping cart dropouts are related to browsing difficulties - lost sales opportunities when the customer has almost reached his or her goal. In terms of direct impact on conversions, according to another study relayed by Google and TrackAd, an extra second of loading time on cell phones represents: +8.3% bounce rate, -3.5% conversion rate, -9.4% page views. Naturally, the effects of a slow website - or worse, if it does not respond because it is overloaded - can be even more damaging during promotional periods.
Moreover, Internet users are not alone in expecting a website to be fast. Google also takes this criterion into account in its algorithm, and to an even greater extent with the Core Web Vitals. These are metrics that evaluate the quality of the UX by observing the loading speed of pages.
Page speed and SEO: Core Web Vitals in the spotlight
In the SEO community as well as in the webperf community, Core Web Vitals have been stirring minds since spring 2020. These are the three following user-centric indicators that Google integrates into the signals it takes into account for the ranking from its Page Experience update in 2021: Largest Contentful Paint (to evaluate display speed), Cumulative Layout Shift (to evaluate visual stability) and First Input Delay (to evaluate interactivity).
Though the impact of loading speed on SERP rankings is still a matter of debate, in a competitive environment it has a clear comparative advantage. Indeed, the faster the pages are, the more Google can index a large number of them in a minimum amount of time, the more likely they are to be ranked higher than pages that would be slower.
In summary, to promote SEO, in addition to the server response time that can be monitored through an indicator called Time To First Byte, the Frontend must also be optimized. Indeed, the image compression, the reduction of the weight and number of requests (optimization of CSS, JS, HTML files...) -and the reduction of the weight of the pages in general- are important both for the user experience and for the search engine robots.
This is all the more relevant since September 2020, Google has switched to mobile indexing first. Just like visitors to a website, the search engine is keen to have pages load quickly on mobile, a device that is more difficult to optimize.
The need to speed up a website and make it mobile first
The speed of web pages depends of course on the way they are designed, but unfortunately there are some factors that are impossible to control: the power of the visitor's cell phone processor, and the quality of the network. This is the reason why a mobile website is more difficult to optimize than a desktop website, whose processors are more powerful and the connection generally more stable. Therefore, for effective optimizations on a mobile phone, you have to think about all users, even the lowest-income users.
As mobile usage grows (75% of the French will own a smartphone in 2018), the power of networks and processors increases, but web pages are not lighter. In October 2000, the average weight of a web page was 89 KB, including images and scripts, whereas today, an average page weighs 2 MB (images make up an average of 50% of their weight). This is a multiplication by almost 30 in 20 years! And this may seem contradictory, knowing that for some retail outlets, mobile phones can represent an overwhelming share of visits and deals.
In order to satisfy and maintain customer loyalty, and to facilitate Google's work, here are some methodological points for a first mobile website. For this, it is necessary to define a performance budget, in other words, performance thresholds not to be exceeded, or scores to be reached (maximum page weight, speed index, time to interactive, PageSpeed score...). It is also important to carry out tests on average or entry-level phones, considering that an audience is not always mostly equipped with recent or powerful models. Finally, it is necessary to carry out tests taking into account network limitations, as a mobile website may run faster using either Wi-Fi or 4G, but it is also necessary to take into account the low latency for users connected in 3G or Edge. Free online tools are available to test the speed of web pages on cell phones, such as Web Page Test, Google's Test My Site, PageSpeed Insights....
La vitesse des pages web est bénéfique pour la satisfaction client, le référencement, et l'indexation mobile. Et ce n'est pas tout: c'est aussi un atout pour absorber le poids des third parties.
Fast pages to better handle third parties
Advertising, A/B test, trackers, search or chat functionalities... In 2019, nearly 94% of web pages on the desktop have at least a third party resource, according to a study by HTTP Archive. These third parties bring value to a website, they are often a must for marketing and they can be a source of income in their own right (media advertising, for example). But they can double or even triple the access time to certain features.
Nevertheless, it is worth noting that depending on the way they are implemented, third-party scripts do not necessarily impair loading times. To take advantage of their benefits without compromising speed and UX, frontend optimization is essential. Pages must be light and scripts prioritized to take up the weight and impact of these third parties. This will allow these value-added services to be integrated without creating a frustrating user experience.
Lastly, in order to know if a website is fast enough, it is also necessary to compare it to its own ecosystem, because depending on the activity field, websites do not have the same intricacy. This is an important benchmark to know where you stand, and what still needs to be done to improve performance.
Loading speed: how to situate yourself in respect to your ecosystem
When it comes to speed, not all markets are at the same stage and do not have the same constraints. For example, advertising revenue is vital for media websites, e-commerce websites need to offer personalized content that meets the needs of their customers... The options and levers for accelerating a website can be different depending on the context. That's why, to know if a website is fast enough, you need to be able to compare it to your competitors.
In the retail sector, for the most visited websites in France, the average Speed Index on cell phones (which measures the speed at which items are displayed above the waterline) ranges from 4520 milliseconds for ready-to-wear to 3077 milliseconds in high-tech. It even reaches 2063 milliseconds on the desktop for the retail sector. In the healthcare pharma sector, websites have a time to interactive (which measures interactivity) on average twice as high, and a speed index on average 39% higher than those of the 50 most visited French websites.
Lastly, in banking-insurance, the response time between an action by the Internet user and the processing of this action by the browser (as measured by the indicator called first input delay, which is part of the Core Web Vitals) is about 0.5 seconds, whereas Google recommends that this time should be less than 0.1 seconds. These KPIs give an overview of the reality of each sector, so that performance comparisons can be made taking into account the reality of a market and its specific business constraints.
To conclude, loading speed is a subject at the crossroads between UX, technical, SEO and business. This is why it must be at the heart of the priorities of all teams, and be the subject of continuous care and work.