UI and UX design: what the difference is and how it affects website sales

UI/UX design in plain terms: UX is about whether a person reaches the purchase without effort, UI is about how it looks and whether it is obvious where to click. Both affect sales from a website, but in different ways: poor UX logic buries the order button below the third screen and adds twelve fields to the form, while weak UI paints that button gray on a gray background so even those who get there do not see it. Below we explain the difference with examples, show how usability eats conversion, and give a 10-point checklist for a quick audit any owner can run in an hour.

UX and UI: what each one is responsible for

UX (user experience) is the path from landing on the site to the desired action, and how logical that path is. UI (user interface) is the interface itself: buttons, fields, colors, typefaces, spacing, hover states. The UX designer decides what to show and in which order; the UI designer decides exactly how to draw it. In small teams this is one person, in large products two separate roles.

The practical takeaway: if people do not buy, look for the problem in UX first. If they buy but complain that the site "looks cheap", the problem is UI. Most often at Query we see a mix: the logic works overall, but there are a few UX holes at key steps plus visual noise that hides them.

How UX problems eat conversion

Three examples that come up in every second audit.

A 12-field form. A consultation request asks for first name, last name, middle name, phone, email, city, company, job title, budget, convenient time, how you heard about us, and a comment. Half of that the manager will ask on the call anyway. Every extra field filters out a share of people, and on mobile the effect is stronger. A working first-contact form: name, phone or messenger, and if needed one question about the task.

CTA below the fold. The homepage has a beautiful banner, then benefits, then testimonials, and only after that an "Order" button. A desktop user may still scroll down; a mobile user leaves earlier. The action button belongs on the first screen, in the header, and should repeat after every content block.

A slow mobile version. The site takes 6 seconds to open, catalog items have no "add to cart" button without opening the product page, filters expand to full screen and close on the third attempt. In our observation, mobile traffic has long dominated in most niches, so every second and every extra tap costs more there than on desktop.

Simpler but no less painful things: no catalog search, prices shown only after registration, the form does not show which field has an error, the "Back" button leads to the homepage instead of the previous step.

The UX design process: research, CJM, prototypes, tests

1. Research. Analytics (where people land, where they leave), session recordings in Microsoft Clarity or Hotjar, 5 to 8 customer interviews, a conversation with sales managers about the questions they hear most. That is enough to see 80% of the problems.
2. CJM. A customer journey map: stages from the first search to a repeat purchase, with thoughts, questions and barriers at each one. It shows what the site lacks before and after the purchase itself.
3. Structure and scenarios. A page map and 3 to 5 key scenarios: find a product, compare, order, get in touch. The number of steps in each becomes measurable.
4. Wireframes and prototype. Black and white screen layouts without visual design, assembled into a clickable prototype in Figma. Changing the logic is cheap at this stage.
5. Usability tests. Five people from the target audience complete tasks on the prototype while thinking aloud. According to the classic Nielsen Norman Group observation, five participants uncover most interface problems. Findings are fixed before the visual design appears.

UI design: design system, accessibility, contrast

Once the logic is verified, the UI designer turns the prototype into mockups. The key deliverable here is the design system: a set of colors, type styles, buttons, fields, cards and rules for using them. It makes the site coherent and makes every next page cheaper, because the developer assembles it from ready components instead of drawing from scratch. How this work looks at an agency is described on our website design page.

Accessibility is not only about people with visual impairments: high-contrast text is readable on a phone in the sun, large tap targets help on public transport, field labels help everyone. The minimum WCAG contrast for regular text is 4.5:1, for large text 3:1, and any contrast checker will verify it. The gray-on-white text fashionable in recent years often fails that bar.

Visual hierarchy: a screen should have one primary action, and it should be the most prominent thing on it. Two identical "Buy" and "Learn more" buttons side by side split attention in half. Element states (hover, pressed, disabled, error) are drawn in the design system, otherwise the developer invents them.

A 10-point express audit

Go through the list on a phone, not on your work computer. Every "no" is a potential point where customers are lost.

1. Within 5 seconds on the first screen it is clear what you sell and to whom.
2. The primary action button is visible without scrolling and repeats further down the page.
3. The page opens in under 3 seconds on a mobile connection (check in PageSpeed Insights).
4. The first-contact form has no more than 3 or 4 fields, and errors are highlighted next to the field.
5. The phone number in the header is clickable, messengers open in one tap.
6. Prices, or at least a price range, are visible without registration or a call.
7. The catalog has search, filters work without a page reload and do not break on mobile.
8. Text is readable: sufficient contrast, at least 16px on mobile, short paragraphs.
9. Nothing covers the content: no popups in the first seconds, no chat widget on top of the button.
10. From any page it is clear where you are and how to go back: the logo leads to the homepage, there are breadcrumbs, the "Back" button behaves as expected.

If you count three or more "no" answers, a full UI/UX design audit with session recordings and a prioritized list of fixes is worth it. We covered the basic usability rules separately in our article on website usability.

Which metrics an owner should watch

• Conversion rate. The share of visitors who completed the target action: order, request, call. Look at it separately for mobile and desktop and by traffic source. A several-fold gap between devices almost always points to mobile problems.
• Pages per session. High depth without conversion often means people are searching and not finding.
• Bounce rate and engaged sessions. GA4 replaces classic bounces with engagement rate. Low engagement on ad landing pages signals that the promise in the ad does not match the page.
• Time to action. How long passes between landing and a button click or form submission. If that is minutes on a simple landing page, the path is too long.
• Form completion. How many people started filling in the form and how many submitted it. A drop at a specific field is visible in session recordings.
• Clicks into nothing. Rage clicks and dead clicks in Clarity: people tap on something that looks like a button but is not one.

Mistakes that keep repeating

• Design for the owner, not the customer. The homepage tells the company's story instead of answering the visitor's questions.
• Redesign without data. The site gets redrawn because it "looks dated", and the old problems move into a new wrapper.
• Copying a competitor. Their interface may be just as accidental as yours.
• Testing on yourself. The team knows where everything is and cannot see what a newcomer trips over.
• Everything at once. Ten equally weighted buttons and banners on one screen. When everything is important, nothing is.

Where to start

1. Go through the 10-point list on a phone and write down every "no".
2. Install Microsoft Clarity (free) and watch 20 session recordings on your key page.
3. Cut the first-contact form to 3 or 4 fields and move the action button to the first screen.
4. Check the contrast of text and buttons and fix anything below 4.5:1.
5. Compare mobile and desktop conversion over a month: a several-fold gap tells you where the big changes should begin.