DoHSpeedTest is a client-side web application that benchmarks DNS-over-HTTPS (DoH) servers directly from the user's browser. It measures round-trip times for DNS queries against a configurable set of hostnames and DoH servers, providing min/median/avg/max response times, reliability scoring, and visual charts. The application runs entirely in the browser with no server-side code, using the fetch API and performance.now() for timing. It includes a warm-up phase to mitigate TCP/TLS handshake overhead, a 5-second timeout per query, and a penalty mechanism for failed requests. Users can customize test hostnames and DoH servers, with settings persisted in localStorage. The architecture is a single-page application (monolith) with one HTML file and one JavaScript file, relying on external CDN dependencies (Tailwind CSS, Chart.js, GitHub buttons). The code demonstrates non-obvious skill in DNS wire format construction, DoH protocol handling, and client-side benchmarking, and includes a comprehensive test suite using Node's vm module for sandboxed execution.