The series markers are painted into a single <canvas> while the axes, grid, zoom selection, legend, and shared tooltip stay as SVG. With renderer: 'auto' the canvas layer switches on once the rendered-mark count crosses rendererThreshold (8,000), so 2,000 points draw as SVG and 10,000+ promote to canvas. Switch the Renderer control to svg at 50,000+ points to feel the difference: the DOM-node count jumps from a few dozen to one node per marker.