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alex / what-happens-when

An attempt to answer the age old interview question "What happens when you type google.com into your browser and press enter?"

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What happens when you type google.com in your browser and press Enter

Tamunoib opened this issue · comments

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When you type https://www.google.com into your browser and press Enter, several steps occur behind the scenes to display the Google homepage. Let's walk through each step in the process:

  1. DNS Request: The first step is to resolve the domain name www.google.com to an IP address. This is done through the Domain Name System (DNS). Your browser sends a DNS request to a DNS server, which then looks up the IP address associated with the domain name.

  2. TCP/IP: Once the IP address is obtained, your browser establishes a TCP (Transmission Control Protocol) connection with the server at that IP address. TCP ensures that the data is reliably transmitted between your browser and the server.

  3. Firewall: The request and response may pass through one or more firewalls, which are network security systems that monitor and control incoming and outgoing network traffic based on predetermined security rules.

  4. HTTPS/SSL: If the website uses HTTPS (Hypertext Transfer Protocol Secure), a secure connection is established using SSL (Secure Sockets Layer) or its successor, TLS (Transport Layer Security). This encrypts the data exchanged between your browser and the server, protecting it from eavesdropping and tampering.

  5. Load Balancer: Large websites like Google often use load balancers to distribute incoming traffic across multiple servers. This improves performance and ensures that no single server becomes overwhelmed.

  6. Web Server: The request is then passed to a web server, which processes the request and generates a response. The web server may retrieve data from a database or perform other tasks to generate the content of the webpage.

  7. Application Server: In some cases, the web server may pass the request to an application server, which executes application code (such as server-side scripts or programs) to generate dynamic content.

  8. Database: If the webpage requires data from a database, the application server retrieves the data from the database server and incorporates it into the webpage before sending it back to the web server.

  9. Response: Finally, the web server or application server sends the generated webpage back to your browser as an HTTP response. Your browser then renders the webpage based on the HTML, CSS, and JavaScript code it receives.

In summary, when you type https://www.google.com into your browser and press Enter, a series of steps involving DNS resolution, TCP/IP communication, security protocols, load balancing, web servers, application servers, and databases work together to retrieve and display the Google homepage in your browser.