Jun 25

What Happens When You Type google.com in Your Browser?

Have you ever wondered about the complex and network processes that take place when you type a URL into your browser's address bar and hit Enter? The journey from hitting the Enter key to seeing a fully rendered web page involves numerous steps, each critical to delivering the content you requested. Let's dive deep into this fascinating journey and break down the steps involved when you type google.com into your browser.

1. DNS Resolution

Domain Name System (DNS) Lookup

The first step in the process is translating the human-readable domain name (google.com) into an IP address that computers can understand. This involves a DNS lookup.

  • Browser Cache: The browser checks its own cache to see if it has recently queried google.com.
  • Operating System Cache: If not found, the browser queries the OS's DNS cache.
  • Router Cache: The request then goes to your router, which might have its own cache.
  • ISP DNS Server: If the router doesn’t have the information, it forwards the request to the DNS servers provided by your ISP.
  • Recursive Search: The ISP's DNS server performs a recursive search, querying root DNS servers, which direct the request to .com TLD servers, and finally to Google's authoritative DNS servers, which return the IP address for google.com.

2. TCP Connection

Establishing a Connection

Once the IP address is obtained, your browser needs to establish a connection to the server.

  • Three-Way Handshake: The browser initiates a TCP connection with the server using the three-way handshake process:
    • SYN: The browser sends a SYN (synchronize) packet to the server.
    • SYN-ACK: The server responds with a SYN-ACK (synchronize-acknowledge) packet.
    • ACK: The browser sends an ACK (acknowledge) packet back to the server.

This handshake establishes a reliable connection between the browser and the server.

3. TLS Handshake (If HTTPS)

Securing the Connection

If you're accessing a secure website (https://google.com), an additional step, the TLS handshake, occurs to establish a secure connection.

  • ClientHello: The browser sends a ClientHello message to the server, which includes supported cipher suites and a randomly generated number.
  • ServerHello: The server responds with a ServerHello message, selecting a cipher suite and providing its own random number.
  • Certificate Exchange: The server sends its digital certificate, which the browser verifies using trusted certificate authorities.
  • Key Exchange: The browser and server exchange keys or generate session keys using the Diffie-Hellman algorithm.
  • Finished: Both the browser and server send finished messages encrypted with the session key to indicate the end of the handshake.

4. HTTP Request

Requesting the Web Page

With the secure connection established, the browser sends an HTTP request to the server.

  • Request Line: Specifies the HTTP method (e.g., GET), the URL path (e.g., /), and the HTTP version.
  • Headers: Include metadata such as Host (google.com), User-Agent (browser type), Accept (types of content), and more.
  • Body: Optional, used with methods like POST to send data to the server.

5. Server Processing

Handling the Request

The server processes the request:

  • Routing: The server determines which service or application should handle the request based on the URL path.
  • Application Logic: The server executes the necessary application logic, potentially querying databases, invoking APIs, or processing business rules.
  • Response Generation: The server generates an HTTP response, which includes the status line, headers, and body (usually the HTML content of the requested page).

6. HTTP Response

Receiving the Response

The server sends the HTTP response back to the browser.

  • Status Line: Indicates the HTTP version, status code (e.g., 200 OK), and status message.
  • Headers: Provide metadata about the response (e.g., Content-Type, Content-Length, Set-Cookie).
  • Body: Contains the actual content, such as the HTML of the web page.

7. Rendering the Page

Displaying the Content

Upon receiving the response, the browser begins rendering the page:

  • HTML Parsing: The browser parses the HTML document, constructing the Document Object Model (DOM) tree.
  • CSS Parsing: CSS files are fetched and parsed to construct the CSS Object Model (CSSOM) tree.
  • JavaScript Execution: JavaScript files are fetched and executed. These scripts can modify the DOM and CSSOM trees.
  • Layout: The browser computes the layout, determining the size and position of elements based on the combined DOM and CSSOM.
  • Painting: The browser paints the pixels on the screen, rendering the visual representation of the web page.

8. Additional Requests

Fetching Additional Resources

During the initial HTML parsing, the browser discovers additional resources (e.g., images, CSS files, JavaScript files) and sends additional HTTP requests to fetch these resources. These steps involve repeating the DNS resolution, TCP/TLS handshake, and HTTP request/response cycles for each resource.


The process of loading a web page when you type google.com into your browser is a complex orchestration of various network protocols, data structures, and algorithms. Each step, from DNS resolution to rendering the page, plays a critical role in delivering a seamless browsing experience. Understanding this intricate journey helps software engineers appreciate the technologies and optimizations that power the modern web.

--Happy Searching

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