Detailed answer
Canvas is a drawing surface, not a semantic tree of drawn text and controls.
Provide accessible equivalent content and use native HTML controls where possible. A chart may need a text summary and data table. Design the alternative alongside the drawing instead of adding a vague fallback sentence at the end.
Example
<canvas width="400" height="200">Lesson progress chart; the same values appear in the following table.</canvas>
Understanding the behavior
Canvas draws pixels rather than a document structure that assistive technology can interpret as headings, controls or table cells. A visual chart needs an equivalent way to understand its data, and interactive canvas content needs an accessible interaction strategy.
Practical implementation notes
Provide a text summary or data table for a chart, and use native HTML controls around interactive graphics where possible. Merely adding a short label does not convey every relationship in a complex drawing.
How to check it
Read its companion data table or text equivalent without looking at the drawing.
Expected result
The important data remains available beyond the canvas pixels.
Watch out: Pixel-drawn buttons do not automatically get keyboard or accessibility behavior.
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