The Brush section of the sidebar (also Tools > Brush) controls the nib every drawing tool uses.
Change size without leaving the canvas:
| Key | Action |
|---|---|
| [ | Decrease brush size |
| ] | Increase brush size |
Layer arrange and rotate use the same brackets with modifiers — for example Command+[ / ] rotates the layer, and Option+Command+[ / ] moves a layer down or up — so bare brackets always mean brush size.
Each tool remembers its own size — with one exception. If you paint with a 4-pixel Pencil and switch to the Eraser, the eraser keeps whatever size you last used with it (often 1 pixel). Switch back to the Pencil and the 4-pixel size returns. Line, Rectangle, and Oval share one size, so changing the stroke weight on any of them updates all three. The sidebar size control always shows the active tool’s size; there is no separate setting for this — it is simply how brush size works. New documents start every tool at 1 pixel until you change them.
Dithering blends the primary and secondary colours using an ordered Bayer pattern—the classic way to fake gradients with a limited palette.
Drag the Dither control between 0% (pure primary) and 100% (pure secondary); in-between values interleave the two colours in increasingly dense patterns. Dithering applies to the brush tools, the shape tools, and fills.
For a fixed, repeatable texture instead of an ordered Bayer level, use a dither pattern—see Use dither patterns in Dottie on Mac.
Adjust it without leaving the canvas:
| Key | Action |
|---|---|
| , | Decrease dither level |
| . | Increase dither level |
| / | Flip the level (for example 25% ↔ 75%) |
Tip Set the secondary colour to the eraser colour and dither against transparency for soft, broken-up erasing.
With a Force Touch trackpad, a pen tablet, or an iPad used as a Sidecar display with Apple Pencil, brush size can follow how hard you press:
Choose Tools > Pressure > Adjust Brush Size.
Draw with the Pencil, Pen, Eraser, or Airbrush—pressure now sweeps the nib across the full 1–16 pixel range.
Fine-tune the feel with Tools > Pressure > Curve—Ease In stays small until you press firmly, Linear is neutral, Ease Out grows quickly under light pressure—and choose Invert to make harder presses draw smaller. A regular mouse always draws at the chosen size.