What is usability from your user's perspective? And a few tips

Chapter 5 of the SEO from zero guide. Published in November 2019 and revised in August 2026. We have corrected a claim that went out of date: we said only mobile sites benefited from user experience signals in Google. That stopped being true in February 2022, when those signals were extended to desktop as well.

When the goal is to rank a page, you have to keep in mind that each person’s navigation must let them find what they came for quickly and easily. That is what usability is about: making a product or a website easy to reach and easy to use.

You have probably heard of user experience (UX) design. The two terms are similar and interact with each other, but they are worth keeping apart.

User experience design is the sum of every element that makes up a website and the way they work together whenever someone engages with it: content, accessibility, credibility, hardware, software, interaction design, graphic design, quality of the writing, findability, usefulness. And, not least, the feelings and emotional factors that build trust.

Usability is a sub-discipline of UX. And it has one enormous advantage over the rest: it can be measured precisely.

The four principles of a usable interface

To measure usability you start by putting the person at the centre: what do they want to do on your page, and in what context. From there, four principles:

• It should be easy to get familiar with the interface and competent with it on first contact.
• It should be easy to reach the goal by using the site.
• It should be easy to remember how it works on later visits.
• It should be reasonably free of errors.

Applied to an online shop, the process looks like this: the person arrives, understands where they are and browses without effort; it is clear how to add to the basket and how to check out; if they cannot finish the purchase right then, coming back that evening they find what they had already looked at waiting for them; and if an error appears, the error page puts them back on the path instead of stranding them.

Usability can be measured throughout development, from wireframes and prototypes to final delivery. The earlier you measure, the cheaper the fix: a problem caught in a prototype is fixed by moving a box; the same problem caught in production is fixed by rebuilding a template.

Servers

Infrastructure is a usability decision, even if it does not look like one. Two factors:

Speed. How fast your page loads is a ranking factor, as well as a condition for anyone staying. A slow site does not connect: people leave. The server plays a part, but it is not solely responsible — whoever designs and builds influences it as much or more, especially in image weight and in how much code has to be downloaded and executed before anything appears.

Downtime. While a site is down it is completely unreachable. Almost every site has the occasional outage; some have far more. Choosing a reliable provider stops someone shrugging and going elsewhere — which is what they do, rather than coming back later.

HTML

Think of your HTML as part of the experience, not as a technical detail:

Alternative text on images. The alt attribute describes the image for anyone who cannot see it: it helps search engines understand what it shows and, more importantly, it lets a screen reader narrate it to someone with a visual impairment. It is the best effort-to-benefit line of code on the whole web.

A useful 404 page. Broken links happen, especially on large sites. Ideally you check them regularly, but you also want a plan for when someone hits one: a well-designed 404 returns the person to a positive experience instead of leaving them at a dead end.

Semantic structure. Headings in order, lists that are lists, buttons that are buttons. That is what makes keyboard and screen-reader navigation possible and, along the way, what helps the search engine understand the page’s hierarchy when it indexes it.

Visual factors

This is where the designer has the most control:

• Type size and colour. Choose fonts that are easy to read, with high contrast against the background and sizes large enough to be comfortable. If your audience is older or has low vision, go bigger. Contrast is not an aesthetic opinion: it is calculated, and below 4.5:1 for body text there are people who simply cannot read you — it is the first of the seven checks in why web accessibility matters.
• Branding. The logo helps people know where they are. In left-to-right reading, the top-left corner is where they look first.
• Colour. Consistent enough to carry the brand, legible, and able to communicate hierarchy. Never as the only carrier of information: if the only clue that something failed is that it turned red, anyone who cannot distinguish that red never finds out.
• Navigation. Getting from point A — the entry point — to point B — what they came for — as quickly as possible. On larger sites, that includes an internal search that actually works.
• Content. Organised into manageable chunks with headings and subheadings, styled consistently across the site, with clear paragraphs that avoid the wall of text.

Measuring, the part almost nobody does

There are plenty of tools for measuring a site’s usability: free, freemium and paid. Try several until you find one that fits, and let it collect data for long enough. That is where you learn what is really happening: where people click, where they get stuck and where they give up.

One addition that was not settled in 2019: Core Web Vitals, which since 2021 have put numbers on what used to be intuition — how long the main content takes to appear, how much the page shifts while loading, and how long it takes to respond to an interaction (that last one has been measured with INP since March 2024). They are free, they are in the browser and in Search Console, and they do not leave room for arguments about taste.

In summary

Usability is how easily someone interacts with your site. It is part of user experience, but it is not the whole story. It rests on three things: that the interface is understood, that it lets people reach their goal, and that it is remembered on the next visit.

Think ahead: who visits your site? Might they struggle to read your text? Will they feel they are somewhere safe? Then measure, fix and measure again. Never underestimate the value of testing from an early stage.

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