This rabbit hole is a waste of time, as someone who's been down it, you'll find piles of resources claiming CSS and JS flags will give you what you want but it never really gets there.

The only way to actually get true aliased brushes in canvas is implementing a line drawing algorithm manually and drawing down aliased circles like how https://gifpaint.com/ & https://jspaint.app/ do it.

And doing it this way is slooowww in JS

This property is already applied if you inspect the canvas elements. Better solution could be context SVG filters https://stackoverflow.com/a/49357655/342095 https://stackoverflow.com/a/68372384/342095