Tool: Width
Look at any handwritten letter, any brush stroke, any line drawn by a person with an actual implement, and measure its thickness at both ends. It won’t match.
It can’t match. A pen nib held at an angle lays down a wide mark when it travels across the grain and a narrow one when it travels along it. A brush is fat where it’s pressed and thin where it’s lifted. A pencil thickens as the hand bears down on a confident stroke and tapers as it releases. Thickness varies because a line is made by a physical thing being dragged across another physical thing, and those things push on each other by different amounts at different moments.
Now look at a line drawn by a computer. It is exactly two pixels wide from beginning to end. It was two pixels wide at the start, it was two pixels wide through the corner, and it was two pixels wide when it stopped. It is the straight-line graph of a quantity that never changed, which is a strange thing to put in a drawing, and it is the default everywhere, and we have all stopped seeing it.
That is what the Width tool is for. You drag on a stroke and you change its thickness at that point, and only near that point. Do it in a couple of places and the stroke swells and tapers along its length: thick through the belly of a curve, thinning as it runs out toward a terminal.
The effect is out of all proportion to the effort. A logo drawn with constant strokes looks like a diagram. The same logo with even a little width variation looks drawn, and people can’t usually tell you why — they just say the second one looks better, or more expensive, or more finished. What they’re responding to is the ghost of a hand.
There’s a reason this is worth understanding rather than just using. Every
typeface you have ever read is built on it. The reason a serif letter has thick
strokes and thin ones is not decoration; it is the fossil of a broad-nib pen held
at a consistent angle, a physical fact from a thousand years ago preserved in
outlines that no pen has touched in centuries. Even a geometric sans-serif, which
is supposed to have uniform strokes, quietly doesn’t: where the round of an o
meets its sides, the curve is thinned, because if it weren’t, the joint would
read as a dark blot to the eye. The designer put a variation in to defeat an
optical effect that only exists in your head.
Uniform width isn’t neutral. It’s a choice, and it usually reads as machinery. [1]
The mechanic here is worth a sentence, because it’s what makes the tool feel direct. A stroke’s width in this editor is not one number; it’s a profile — a set of widths at points along the path. Dragging with the Width tool adds a point to that profile and sets its value, and the widths in between are interpolated, so the change eases in and out instead of stepping. Which means you are not editing a parameter of the line. You are editing the line, in the place you are pointing at, which is the same principle as Reshape one layer down: act on the region you can see, not on the abstraction that produced it.
And it is still a vector. The stroke isn’t rasterized into a filled blob you can no longer adjust; the profile lives on the path, so you can go back a week later and thin it out. Everything else — moving anchors, reshaping, smoothing — keeps working. Width is a property of the stroke, not a destructive commitment.
Use it sparingly. The failure mode is a drawing where every line pulses like a neon tube and the eye has nowhere to rest. The good version is subtle enough that nobody notices, which is the whole trick — the best compliment a drawing can get is that it looks like someone drew it. [2]
[1] Occasionally you want machinery. Technical diagrams, wiring schematics, anything where the line is carrying information rather than feeling — constant width is correct there, and any variation reads as a meaningful signal that isn’t one. The point isn’t that variation is always better. It’s that uniformity should be a decision.
[2] The other failure mode, which I fall into constantly, is putting width variation on a stroke that had no business being a stroke. If you find yourself fighting a profile to make a shape, the shape wanted to be a filled path. Draw the outline and fill it.