HTML in HTML in HTML — and where it decoheres

Part 1 nests three real documents you can see. Part 2 keeps nesting until your browser refuses, and reports the depth it broke.

Part 1 — a 3-deep nest LIT

Each colored frame is a separate full <!DOCTYPE html> document, built at runtime inside the one around it.

Part 2 — decoherence probe MEASURED LIVE

Same trick, run to the limit: every level phones window.top and spawns the next. When new levels stop reporting for a moment, that's decoherence — your browser's nesting ceiling.

deepest level alive

status

idle

target cap

target depth cap 80

Press Run probe. It nests iframes one inside the next until your browser stops allowing it. High cap = deeper attempt (and briefly heavier on the tab).

Note: the ceiling is browser-dependent — Chromium, Firefox, and Safari each cap nested browsing contexts differently to stop runaway recursion. This measures yours, not a universal constant.