http-request-response-cycle

What actually happens between fetch() and response.json()?

Per Wikipedia: “The request-response cycle is the full round trip — DNS, TCP, TLS, HTTP request, server handler, HTTP response, browser parse.”

Like ordering food — find restaurant address, travel there, place order, wait for kitchen, carry tray back.

1. Resolve host via DNS
2. Open TCP then TLS
3. Send HTTP request line+headers+body
4. Server routes and handles
5. Return status+headers+body

• Stateless per request
• Keep-Alive reuses TCP
• 3 RTT before first byte with TLS

• Built from: HTTP — cycle implements HTTP
• Built from: HTTP Headers — headers travel in cycle
• Related: HTTP Status Codes — status returned
• Builds into: CORS — CORS checked in cycle

• Assuming one TCP per request — keep-alive reuses
• Forgetting preflight in cycle