Load site (headless)
Load a URL in headless Chromium via Playwright and stream every fetched resource with size and timing.
Reports up to 400 resources. Hard wall-clock cap 50 s.
Cross-origin responses without a Timing-Allow-Origin header report size as 0 (browser limitation).
Origin is on an old TLS stack ( only)
negotiated and refuses TLS 1.3. The cert chain itself is fine — this is a handshake-stack issue, not a verification one. Typical fingerprint: older Apache / IIS / Nginx with a modern Let's Encrypt cert grafted on, or a stale load balancer config. Modern Chrome's TLS 1.3 ClientHello (with post-quantum key share, ~1.5 KB) often fails against such servers; we launch Chromium with --disable-features=PostQuantumKyber here so the load can still complete via TLS 1.2.