Your Website on a Smartphone: What Business Customers Expect on Mobile

Do business customers even need a mobile website?

Many B2B businesses hold on to an assumption: our customers sit at desks, they research on large screens, and the smartphone plays no role for us. The assumption is not entirely wrong. But it overlooks what happens between research sessions. The operations manager sees an outage in the hall and quickly searches for a provider. The buyer checks once more who the supplier is before a meeting. A colleague forwards a link via messenger, and it is opened on a phone.

This analysis therefore answers the question: What do business customers expect from a website on a smartphone, and what does a small business need to do for it? We first clarify how Google treats mobile pages and introduce a model from research on screen interaction. Then we look at findings on thumb input, weigh two views on the importance of the smartphone in B2B and derive a simple test.

On a smartphone, what decides is not how much the page offers, but whether the one thing the visitor wants right now works with a thumb.

What mobile display means and why Google assumes it

A responsive website adapts the layout and size of its elements to the screen width, rather than showing a shrunken version of the desktop page. That is the norm today. But it does not follow that the page is easy to use on a smartphone. A page can adapt technically and still show buttons that are too small, tables that run off the side of the screen, or a phone number that cannot be tapped.

For visibility in search, the smartphone has long been decisive. Google declared its mobile-first indexing, meaning crawling and evaluating websites in their mobile version, complete in October 2023 and announced that after July 5, 2024 it would crawl even the last remaining websites only with the smartphone crawler. Whatever is missing from the mobile version, such as a hidden section or a table that appears only on desktop, is therefore also missing for search.

Then there are the load time metrics. The article on website load time describes the Core Web Vitals. A page is considered good if the largest visible element appears within 2.5 seconds, measured across three quarters of visits, and problems usually show up only on a mobile connection.

The thinking model: Fitts’s law

In 1954 the psychologist Paul Fitts studied how long people need to hit a target with a movement. Fitts’s law, named after him, states: the time for an aimed movement increases with the distance to the target and decreases with its size. A large target nearby is hit quickly and reliably; a small target far away slowly and with more errors. The law remains one of the foundations of interface design to this day, including for touchscreens, as a review by Xiao and colleagues (2024) shows.

On a smartphone the model takes a particular form. The thumb is the pointing device, and it is wider and less precise than a mouse pointer. The literature speaks of the fat finger problem. In addition, with one-handed use the thumb does not reach every spot equally well. Targets at the top edge or in the far corner are further away than they look. For a website this means: whatever is used often belongs large and within reach.

There is a guide value for size. The Web Content Accessibility Guidelines WCAG 2.2 require at level AA that targets be at least 24 by 24 CSS pixels or have sufficient spacing. More room is better for the thumb. The article on the accessible website describes when such requirements are mandatory in Germany.

What studies show about thumb input

Kim and Jo (2015) wanted to know how much performance drops with one-handed thumb input under realistic conditions. They recruited 259 people in New York, San Francisco, Paris and London, balanced by gender and age, from under 20 to over 60. Over two days, each person moved an icon on a touchscreen 864 times, once one-handed with the thumb and once with the index finger while holding the device. The targets lay in the four corners, in three sizes, the largest following the design guidelines of a major manufacturer at the time.

The result: with the thumb, throughput, a measure of speed and accuracy combined, fell by 30 percent. The loss came mainly from inaccuracy, less from slowness. How large it was depended on the position and direction of the movement. With thumb input the values varied so much that Fitts’s law predicted them less well than for the index finger. The authors name the limits themselves: the device had a 3-inch screen, the participants were seated, and only dragging was tested, not tapping.

Hayes, Steiger and Adams (2016) add a second finding. They studied how long tapping takes on smartphones when the target is initially off-screen and can only be reached by scrolling. Fitts’s law predicted these times less well than for visible targets; the visibility of the target had a large influence. Applied, this means: a button you first have to find costs more time than its size suggests.

How important is the smartphone in B2B? Two views

The first view considers the smartphone secondary in business-to-business markets. Larger purchases are prepared at the desk, proposals compared on large screens, data sheets printed. In the web analytics of many B2B businesses, a large share of visits does indeed come from desktop computers, especially on weekdays during office hours.

The second view considers it decisive at certain points. The share of visits says little about which visits count. The call after an outage, the check on a supplier just before a meeting or the forwarded link often come via the phone. And because Google crawls the mobile version, it also determines whether a business is found at the desk.

I consider the second view the more accurate one. The question is not what percentage of visits are mobile, but which tasks are done on the go. These tasks must work effortlessly on a smartphone. Everything else may be more convenient at the desk. The device report in web analytics or in Google Search Console shows the share for your own business.

The thumb test: five tasks that must work on mobile

From the model and the findings I derive a simple test that I call the thumb test. It checks five tasks that business customers carry out on the go. Each is performed one-handed with the thumb on your own smartphone and over a mobile network, not the office Wi-Fi.

1. Call

   Call with one tap from the home page and from every service page. The number is a large button, not just text.

2. Understand the service

   The first screen says, without scrolling, what the business offers and for whom. The three-question test applies on mobile just the same.

3. Inquire

   The form can be filled in with the thumb, the right keyboard opens and an error message appears right at the field.

4. Open documents

   Data sheets and price lists open legibly. A landscape PDF with fine print fails the test.

5. Find the way

   Tappable address, link to the map, directions or delivery access where customers come.

Anyone who manages each task in under a minute has passed the test. Whatever takes longer goes on the list. The second task follows the three-question test from the article on a website that brings inquiries: what do you offer, for whom, and what is the next step? The third is covered in depth in the article on the inquiry path on the website.

What to leave out on a smartphone and what to keep?

Mobile design does not mean cutting content. Because Google crawls the mobile version, a section that appears only on desktop harms visibility. It is about order and form: what is needed on the go sits at the top and is large. What is read at the desk may sit further down and be collapsible.

A common mistake is overlays that cover the whole screen on a smartphone, such as a large newsletter window on the first visit. On the small screen the close icon is often the smallest target on the page. According to Fitts’s law, that is the worst combination: a small target you have to hit first.

The lesson beyond the case

The mobile website illustrates a general principle: customers judge a business at the moment they need it, and with the device they happen to be holding. A business that cannot be reached on the go does not seem modern or old-fashioned, but unreachable. That affects trust as much as inquiries. Anyone who runs the thumb test once a quarter notices deterioration before customers do.

The limits lie in the evidence. The experiments on thumb input used older, smaller devices and seated participants, so rather favorable conditions. I found no reliable figures on the share of mobile research in German B2B, so this article works with a worked example and the advice to read your own figures. Fitts’s law and Google’s crawling are robust.

Conclusion and a first step

The guiding question was what business customers expect from a website on a smartphone and what a small business needs to do for it. They do not expect every piece of research to be convenient on mobile. They expect five things to work effortlessly: calling, understanding the service, inquiring, opening documents and finding the way. According to Fitts’s law, that means important targets large and within reach of the thumb, and no small hurdles in front of the content. Because Google crawls the mobile version, every piece of content that matters for search also belongs on the smartphone. On mobile, what counts is not the share of visits but which visits they are.

• Run the thumb test with the five tasks on your own smartphone over a mobile network.
• Check whether the phone number is a tappable button on every page.
• Break down the device report in web analytics or Search Console by source.
• Open data sheets on a smartphone and check whether they are legible.
• Turn off or shrink overlays on the first visit on smartphones.