Your Site Is Up. Your Site Is Broken. Both Are True.

Every monitoring tool on the market will tell you when your site is down. None of them will tell you when your site returns HTTP 200 OK but serves a broken experience. We built Sitewatch to close that gap. This post covers the detection engineering behind it — what we check, how we confirm failures, and why traditional uptime monitoring has a fundamental blind spot. The Problem: 200 OK Is Not "OK" A standard uptime monitor sends an HTTP request, gets a 200 status code, and marks your site as healthy. But a 200 response tells you almost nothing about whether your site actually works. Here are real failure patterns that return 200 OK: A Vercel deploy changes your bundle hash. main.a4f2c.js now 404s, but the HTML document still returns 200. Your app shell loads. Nothing renders. Cloudflare serves app.js with Content-Type: text/html instead of application/javascript . Chrome silently blocks execution. The page loads — with zero interactivity. A WordPress plugin misconfigures redirects. /ch