What happens when you type a URL into a browser and press Enter?

Summary

The browser parses the URL, checks caches, resolves the domain through DNS (browser, OS, resolver, root, TLD and authoritative servers), opens a TCP connection (or QUIC for HTTP/3) to the IP, performs a TLS handshake and validates the certificate, sends the HTTP request, which passes through CDNs, load balancers and proxies to an application server that may call databases and caches, then receives the response and renders the page, fetching more resources.

Longer Answer

A DevOps-flavoured answer adds where things go wrong and how you would see it: DNS misconfiguration or TTL issues, expired certificates, load balancer health checks removing all targets, connection limits, slow upstream dependencies, CDN caching headers. Mention HTTP keep-alive and connection reuse, redirects (HTTP to HTTPS), cookies, and the tools you would use at each layer (dig, curl -v, openssl s_client, load-balancer logs, traces).

Key Points

• URL parse, cache, DNS resolution.
• TCP/QUIC, TLS handshake, certificate check.
• HTTP through CDN, LB, proxies to the app.
• Know failure points and tools per layer.

What interviewers look for

Breadth across layers and, for DevOps roles, how to debug each one.