What Happens After Entering a URL in the Browser?

What Happens After Entering a URL in the Browser?

• 1. DNS Resolution Phase (Obtain Target Server IP)
  • Check if there is a DNS cache available
  • Query the local DNS server provided by the ISP
• 2. TCP Connection Establishment (Establish Connection with Target Server)
  • Initiate TCP connection request to the target IP address
  • Perform TCP three-way handshake (SYN, SYN-ACK, ACK)
• 3. TLS/SSL Encrypted Connection (Establish Encrypted Connection with Target Server)
  • Perform handshake and exchange encryption keys
  • Validate certificates
• 4. Request and Response (Retrieve Web Content)
  • The browser sends a request to the server
  • The server processes the request and returns resources
  • The browser begins to receive and parse resources
• 5. Browser Rendering Page (Render Web Page)
  • Parse HTML to create DOM Tree
  • Parse CSS to create CSSOM Tree
  • Combine DOM and CSSOM to create Render Tree
  • Calculate element positions and sizes (Layout)
  • Paint the page content (Paint)
  • Divide the page into multiple layers (Layering)
  • Convert layers to pixels (Rasterization)
  • GPU composites multiple layers (Compositing)

Depending on the position, one can gradually identify the areas of interest through communication. For instance, front-end developers may be eager to learn more about how browsers operate. I believe back-end friends also have different focal points on this topic.