Revision Sheet
HTTP Contracts
Requests and responses carry intent, identity, freshness, content type, cache policy, redirects, and browser security context.
Network Lifecycle
DNS, connection setup, TLS, HTTP versions, redirects, and resource discovery shape page speed before React code runs.
Trust Boundaries
CORS, credentials, same-origin policy, CSP, storage, iframes, and sandboxing define what browser code can read and do.