Phase 1: Translating Names to Addresses via DNS
When you enter a web URL into a browser address bar, the machine does not instinctively know where that server resides. It initiates a hierarchical Domain Name System (DNS) query.
The browser checks local cache, queries the operating system resolver, contacts recursive resolvers, and inspects root and authoritative name servers to translate human-friendly domain names into numerical IP addresses.
Phase 2: Establishing Secure Transport (TCP & TLS)
Once the IP address is resolved, the client opens a TCP socket connection via a three-way handshake (SYN, SYN-ACK, ACK).
Immediately following TCP connection establishment, a Transport Layer Security (TLS) handshake takes place: cryptographic certificates are authenticated, public key algorithms negotiate ephemeral session keys, and encrypted communication begins.
Phase 3: The Critical Rendering Path
Upon receiving the HTML byte stream from the server, the browser parser converts raw bytes into characters, tokens, nodes, and finally the Document Object Model (DOM) tree. Concurrently, CSS styles are compiled into the CSSOM tree.
The layout engine computes exact coordinate geometries for every element before painting pixels to the display raster buffer.