Look at a page without trusting it.
The file renders inside a frame that cannot run scripts, and every reference that would fetch something is removed first — so looking at a page someone sent you does not tell them you did. Switch the external assets back on when you want the real thing, or read the source and the heading outline instead.
.html file hereFiles you open are remembered here, on this device, and are listed by every viewer. Nothing is sent anywhere — clearing them is permanent.
Scripts are blocked by the sandbox, and scripts, stylesheets, images and frames pointing anywhere else are stripped before rendering, so nothing is fetched. One click switches them back on.
Rendered, highlighted source, and an indented outline of every heading in the document.
The PDF button prints the rendered frame itself, so the page comes out looking like the page.