usefulweb.site The Compatibility Engine

Contracts, safety & accessibility

The Compatibility Engine

Will this charger, cable, version or PC part work together? Rule-based checks with margins.

W

Charging mode.

W

Semver mode. npm syntax.

PC mode.

W
W
W
W
%

Try an example: 140 W laptop on a 100 W charger · Node.js engine range · AM5 gaming PC

How it works

Three deterministic checks: (1) USB-C charging – the real maximum power from charger, cable and device per the USB Power Delivery rules; (2) software versions – whether versions satisfy an npm-style semver range (^, ~, x-ranges, hyphen ranges, ||); (3) PC builds – CPU socket, RAM generation, slots and power-supply headroom.

  • Charging: with USB PD on both sides the standard power range allows 5/9/15/20 V at 3 A (≤ 60 W with a standard cable) and 20 V at 5 A (≤ 100 W) with a 5 A e-marked cable; above 100 W (28/36/48 V, ≤ 240 W) needs charger, device AND cable to support PD 3.1 EPR. Without PD on both sides the assumed ceiling is USB-C 5 V / 3 A = 15 W. Expected maximum = minimum of charger, device and that limit.
  • Semver: npm range semantics (^ caret, ~ tilde, x-ranges, hyphen ranges, || alternatives, comparator sets); prereleases only match ranges that mention a prerelease of the same version.
  • PC: sockets must match exactly (case-insensitive); RAM generation must match; modules ≤ slots; recommended PSU = (CPU + GPU + other) × (1 + headroom%).

For scripts and AI agents

  • JSON API: POST https://compatibilityengine.usefulweb.site/api/v1/calculate (same calculation as this page)
  • Interface description: OpenAPI 3.1 · AI guide: llms.txt
  • MCP server (Streamable HTTP): https://compatibilityengine.usefulweb.site/mcp · tool name compatibility_engine
Example request
curl -s -X POST https://compatibilityengine.usefulweb.site/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"mode":"charging","chargerW":100,"chargerPd":true,"deviceW":140,"devicePd":true,"deviceEpr":true,"cable":"usb-c-3a"}'

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