Font loading: a practical guide

This is cheap to get right at the start and expensive to retrofit. This guide covers what font loading actually involves, where it usually goes wrong, and how to tell whether yours is in reasonable shape.

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. 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

Custom fonts commonly block the first paint. In practice this is a scheduling problem more than a technical one. If it only works because one person remembers to do something, it does not work yet.

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. That sounds obvious written down. It is still the thing most often skipped.

Where to start

Self-hosting removes a third-party round trip. Getting it slightly wrong is survivable. Ignoring it entirely is not. The teams that stay on top of it are the ones who put it on a calendar rather than a wish list.

Performance work is mostly subtraction, which makes it unpopular and effective. The version that works in practice is usually less elaborate than the version described in the guides.

A sensible fallback prevents invisible text. Getting it slightly wrong is survivable. Ignoring it entirely is not. It is the sort of thing that looks like polish right up until it costs you an enquiry.

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.

• Custom fonts commonly block the first paint
• Self-hosting removes a third-party round trip
• A sensible fallback prevents invisible text
• 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

Common failure modes

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

Speed is a feature people notice only in its absence, and then they leave rather than complain. 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?

Where to go from here

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.