A fully browser-based Intel 80486DX2-66 emulator now exists, built by Jan de Jager and written entirely in ES6 JavaScript. It emulates not just the CPU but the full system: motherboard, ISA and VLB adapter cards, VGA BIOS, and SeaBIOS. It runs FreeDOS 1.3 and boots Wolfenstein 3D, Duke Nukem, and DOOM inside a single browser tab.
The project ships with a control panel for configuring storage and expansion cards. No download, no install, no compatibility check against your host OS. The entire stack lives at github.com/jandej/e486-web. What makes the full write-up worth reading is the detail on how ISA and VLB bus emulation was handled in JavaScript, where the real complexity of matching period-accurate hardware behavior lives.
Browser-based emulation has quietly crossed a threshold. The CPU cycles that once made this category of software a dedicated application are now trivially available in a tab. The next question the community is already asking: how far down the hardware stack can JavaScript go before it hits a wall.
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