Accessibility usually gets treated as a testing task near the end of a project, which is roughly like checking whether a building has wheelchair access after the concrete has set. It is much cheaper, and the result is much better, when it shapes the structure from the start. Here's what that actually involves, in practical terms rather than legal ones.
What we're actually talking about
Accessibility gets discussed as if it were solely about screen readers, and screen reader users matter, but they're a small part of it. The bigger group is people using your site in ordinary conditions that happen to be difficult.
Someone reading on a phone in bright sunlight. Someone with a hand injury using a keyboard only. Someone in their seventies whose eyesight has changed. Someone who is stressed, distracted, or trying to find your opening hours while driving. All of them benefit from the same decisions.
That's why it's worth doing regardless of any obligation. The changes that make a site work for someone using assistive technology are, almost without exception, changes that make it work better for everybody.
Where it belongs in a project
The decisions that matter most happen early, before anything is designed. How the content is structured. What the heading hierarchy is. Whether the navigation makes sense when read out one item at a time. Whether a form can be completed without a mouse.
Those are structural, and they're nearly free at the planning stage. Retrofitting them after the design is signed off means redoing the design, which is why accessibility gets dropped from budgets. It's not expensive to build in; it's expensive to add.
The second cluster of decisions is in the visual design, mostly around colour contrast and text size. Also cheap at the right moment, also awkward afterwards, because changing a brand colour late affects everything.
The things that go wrong most often
Colour contrast is the most common failure by a distance. Light grey text on white looks refined in a design tool and becomes unreadable on a laptop screen in a bright room. It's also the easiest thing to check.
Second is form labels. Placeholder text inside a field disappears the moment someone starts typing, which is a problem for anyone who gets interrupted, and it's invisible to screen readers in some combinations.
Third is keyboard navigation. Try getting through your own site using only the tab key. If you can't tell where you are on the page, or you get stuck inside a menu you can't escape, that's a real problem for a real group of people.
Fourth is images with no alternative text, or alternative text that says image of a photo. Describing what the image is for takes ten seconds per image and is usually skipped.
What it costs
Built in from the start, accessibility adds very little to a project. Some extra care in the design phase, some testing time before launch, and a developer who knows what they're doing. On a typical project it's a rounding error.
Added afterwards as a remediation exercise, it can cost a significant fraction of the original build, because it means revisiting decisions that everything else was built on top of.
The honest way to think about it is that it's not a line item at all. It's a way of working, and studios that treat it as an optional extra are usually telling you something about how they build.
What to ask a studio
Ask what standard they build to, and whether they test with a keyboard and a screen reader or only with an automated tool. Automated tools catch perhaps a third of real problems and miss most of the ones that matter.
Ask to see the CMS. A site that launches accessible and then degrades as staff add content over two years is very common, and the fix is an editing interface that makes the right thing easy.
Ask what happens if something fails after launch. A studio that has thought about this will have an answer ready.
If you're a public body or a charity
The obligations are more specific and worth getting proper advice on, because they vary by sector and by the nature of the organisation. In Ireland the European Accessibility Act has applied since June 2025 to a defined set of consumer-facing services, and public bodies have had their own duties for longer under the Web Accessibility Directive. EN 301 549 is the standard both point at.
More practically, if your audience includes people who are unwell, elderly, in crisis, or using a public library computer, the case for doing this properly doesn't rest on legislation at all.
Budget for it explicitly rather than assuming it's included, and ask the question early enough that the answer can still change the plan.