How the lockdown works

Six independent layers, so no single mistake opens a hole.

1. An allowlist per site. Each entry lists the only hosts allowed to load anything at all. Every other request is cancelled: image, script, frame, websocket. This layer does most of the work: it blocks ad networks nobody has heard of yet, because they are not on the list.

2. An ad and tracker blocklist. ~110 known ad, tracker and popunder domains plus URL patterns, checked even on allowed hosts. This catches ad code served from a site’s own CDN, which an allowlist alone cannot see.

3. No new windows. Every popup, target="_blank" and window.open is denied. If the link was to an allowed page it opens in place instead, so nothing appears broken.

4. No navigating away. Any attempt to move the page, a frame, or a redirect to a non-allowlisted host is cancelled. Non-web schemes (mailto:, steam:, file:) are refused, so no page can launch another program.

5. No keyboard escapes, but games keep their keys. A page-level filter swallows modifier combinations, function keys, devtools and reload. A second OS-level layer takes 64 shortcuts away from the window manager itself, including Cmd/Alt+Tab, Mission Control and Spotlight.

What still reaches the game: arrow keys, WASD and every other letter, the digits, space, Enter, Escape, and Ctrl or Shift pressed on their own. A modifier held by itself is a game action; only a modifier combined with another key is a shortcut. The page is given keyboard focus on load and whenever it returns from the exit gate.

6. Nothing else. Downloads cancelled. Right-click, devtools and alert() traps disabled. All permissions denied except fullscreen and pointer lock. No app menu. Bad certificates never overridable. Its own browser profile, entirely separate from yours.