CSS architecture: a practical guide

The version of this that works is simpler than the version most people imagine. This guide covers what CSS architecture actually involves, where it usually goes wrong, and how to tell whether yours is in reasonable shape.

Code gets read far more often than it gets written, and usually by someone with less context than the author had. 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 it matters

Naming conventions prevent the specificity arms race. Getting it slightly wrong is survivable. Ignoring it entirely is not. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

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. None of that requires a large budget, only a decision and someone to own it.

The practical version

Custom properties centralise the values you change most. The cost of getting this wrong is rarely visible on the day it happens. The teams that stay on top of it are the ones who put it on a calendar rather than a wish list.

Most development decisions are really maintenance decisions wearing a different hat. The version that works in practice is usually less elaborate than the version described in the guides.

Deleting CSS should be as easy as adding it. 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.

• Naming conventions prevent the specificity arms race
• Custom properties centralise the values you change most
• Deleting CSS should be as easy as adding it
• 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

The question is rarely whether something can be built, but what it costs to keep running afterwards. In practice this is a scheduling problem more than a technical one.

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?

Turning this into a decision

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 are not sure where your systems currently stand on this, it takes us about an hour to find out.