Alt text: a practical guide

We end up explaining this on discovery calls often enough that it deserved writing down. This guide covers what alt text actually involves, where it usually goes wrong, and how to tell whether yours is in reasonable shape.

Accessibility work almost always improves the experience for people who have no impairment at all. Nothing below assumes a large team or a large budget — most of it is a decision somebody has to make and then write down.

Why this earns attention

Describe the purpose, not the appearance. In practice this is a scheduling problem more than a technical one. It is the sort of thing that looks like polish right up until it costs you an enquiry.

For most businesses the question is not whether this matters but how much of it is worth doing right now. That depends on what you are trying to achieve in the next few months, not on best practice in the abstract. In practice this is a scheduling problem more than a technical one.

What good looks like

Decorative images should have empty alt attributes. Where this goes wrong is almost never a lack of knowledge. If it only works because one person remembers to do something, it does not work yet.

The cost of retrofitting accessibility is several times the cost of building it in. The version that works in practice is usually less elaborate than the version described in the guides.

Never start with "image of". Getting it slightly wrong is survivable. Ignoring it entirely is not. It is worth deciding this deliberately rather than inheriting whatever the last person set up.

A working checklist

If you want a quick read on where you stand, work through this. Anything you cannot answer confidently is where to start.

• Describe the purpose, not the appearance
• Decorative images should have empty alt attributes
• Never start with "image of"
• Someone is named as the owner, not just assumed to be
• There is a date in the calendar to review it again
• The decision and the reasoning behind it are written down somewhere findable
• You could explain the current setup to a new hire in five minutes

The mistakes we see most

The most common failure is not doing this badly. It is doing it once, during a launch, and never revisiting it. Circumstances move, the setup does not, and the gap widens quietly until something breaks or somebody notices the numbers.

• It was configured during a launch and has not been touched since
• Different people in the business believe different things are true about it
• There is no way to tell whether the last change helped or hurt
• The only person who understands it has left, or is about to

Most of it is correctness rather than charity: use the right element and much of it happens automatically. Where this goes wrong is almost never a lack of knowledge.

How we approach it

On our projects this gets handled during the build rather than added afterwards, because retrofitting it costs several times more than including it. We write down what was decided and why, so the next person to touch it is not guessing.

If you are working with someone else, the questions worth asking are simple: who owns this, how will we know it is working, and what happens when it needs to change?

What to do next

Pick the single item from the checklist above that would cause the most trouble if it turned out to be wrong. Fix that one, confirm it worked, then move on. If you want a second opinion on how yours is set up, ask.