Canvases
Every canvas's size, pixel ratio, drawing context and main colours.
These cards are in the Design tab. Hover a row to outline its element on the page, and click it to select it, which fills the Element tab.
Canvases lists every canvas on the page: its size in device pixels, the pixel ratio (a ratio of 1 on a sharp screen is a blurry canvas), the drawing context (2D, WebGL, WebGL 2 or Bitmap) and the colours it is mostly made of, as swatches you can hover for the share of each.
Nitpique reads a canvas without changing it. A canvas that reads Empty, or drawn by a worker has nothing the page's own code has drawn on it. Its context stays unset, so the page can still choose one; a canvas a worker draws on cannot be told apart. A WebGL canvas that does not keep its buffer can read as empty too, and one showing another site's pixels cannot be read for colours.
Questions
Does reading a canvas change it?
No. Nitpique reads a canvas without changing it, and leaves an unset context unset so the page can still choose one.
Why is my canvas blurry?
Check its pixel ratio: a ratio of 1 on a sharp screen is a blurry canvas.