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

The vast majority of internet users have, at some point during their online endeavors, entered "https://www.google.com" into a web browser. Have you ever wondered about the sequence of events that unfolds once you press the enter key? If you have, I'll explain it to you.

Rather than skimming the surface, I'll dive into the details so you can gain a comprehensive understanding and technical proficiency in how the web operates. Don't worry—I'll simplify everything for easy comprehension.

Assuming you're familiar with the term "browser," if not, that's okay. A browser is an application that allows internet access, such as Google Chrome, Firefox, Vivaldi, Safari, Opera, Edge, etc.

When you input a URL (uniform resource locator) like "https://www.google.com" into your web browser (e.g., Chrome) and hit enter, several actions take place before any output appears on your browser. Fortunately, these actions occur almost instantly, so there's little time to dwell on them. Before delving into the steps and elaborating on them, let me give you a brief overview of the processes happening within those few microseconds.

Your computer sends a request to the domain name system (DNS) server, acting as an address book for all domain names. The DNS server then returns the specific IP address associated with the server pointed to by "https://www.google.com."

With this IP address, your computer establishes a connection with the server using the TCP (Transmission Control Protocol), facilitated by the IP (Internet Protocol). This process is termed a "handshake."

If your computer is behind a firewall, it verifies the authorization of your request before granting it. Similarly, if the server is behind a firewall, a similar check occurs before you can connect.

Once the connection is established, your browser sends a request for the webpage using a security protocol like SSL (Secure Sockets Layer) or TLS (Transport Layer Security) to encrypt the data exchanged between your computer and the server. This encryption is denoted by the "s" in "https" (Hypertext Transfer Protocol Secure), signifying a secure connection.

To manage high traffic, companies like Google employ multiple servers and use a load balancer to distribute requests. The load balancer receives your browser's request and directs it to a specific server based on its algorithm.

The server responds to the load balancer, which then relays it back to your browser. The response typically includes HTML (Hyper Text Markup Language), CSS (Cascading Style Sheets), and JavaScript files constituting the webpage. HTML guides the browser on displaying content, CSS styles it, and JavaScript adds interactivity.

For dynamic content like Google search results, the web server may request it from an application server, which could then seek data from a database server. The web server incorporates this data in the response sent back to your browser. Finally, your browser renders the webpage and displays it to you.

Were you aware of the myriad activities preceding the appearance of anything on your web browser? This is a condensed summary of the process. Now, let's explore each step in detail.

DNS Lookup Process

The DNS (Domain Name System) plays a pivotal role in enabling users to access websites seamlessly by translating human-readable domain names into machine-readable IP addresses. Understanding the DNS lookup process enhances our appreciation for the intricacies involved before a webpage is displayed.

1. Browser Initiates DNS Request:

- When you input a URL like "https://www.google.com," the browser initiates a DNS request to the local DNS resolver, often provided by the ISP.

2. Local DNS Resolver Checks Cache:

- The local DNS resolver checks its cache for the most recent DNS record. If found, it promptly returns the IP address to the browser.

3. Root Nameserver and TLD Nameserver Involvement:

- If the DNS record is not in the local cache, the resolver queries a root nameserver and then a top-level domain (TLD) nameserver, such as ".com."

4. Authoritative Nameserver Interaction:

- The TLD nameserver directs the resolver to the authoritative nameserver for the domain.

5. Final IP Address Retrieval:

- The local DNS resolver sends a request to the authoritative nameserver, which responds with the IP address for the domain.

6. IP Address Sent to Browser:

- The local DNS resolver sends the IP address back to the browser, enabling it to proceed with establishing a connection.

7. Browser Requests Webpage:

- Now armed with the IP address, the browser sends a request to the server at that IP address to retrieve the webpage.

8. Additional Considerations:

- The DNS lookup process may involve more steps if DNS records are not found or if DNS load balancing or content delivery networks (CDNs) are in use.

- The "Time To Live" (TTL) for DNS records, determining how long the record is cached, is set by the authoritative nameserver.

TCP/IP Connectivity:

While DNS resolves the domain, TCP/IP ensures the reliable and ordered exchange of data between the client (browser) and the server.

1. Browser Sends IP Request:

- The browser uses IP to send a request to the server to establish a connection.

2. Handshake Procedure:

- The server acknowledges the connection request through a handshake procedure, facilitated by TCP.

3. TCP for Reliable Request and Response:

- With the established connection, the browser uses TCP to send a reliable and sequenced request for the webpage.

4. Server Responds Using TCP:

- The server, utilizing TCP, responds with the HTML code for the webpage, ensuring dependable transmission.

5. Displaying the Webpage:

- The browser receives the HTML code, using it to display the webpage on the user's screen. Any additional resources, such as images, are also requested and received using TCP/IP.

In essence, the DNS lookup process and TCP/IP connectivity work hand-in-hand to translate domain names, establish connections, and facilitate the secure and ordered exchange of data, ensuring a seamless user experience on the internet. This holistic understanding underscores the collaborative efforts of these processes in bringing web content to users with efficiency and reliability.

Firewall Protection:

In the digital realm, a firewall stands guard as a security sentinel, meticulously overseeing both incoming and outgoing network traffic. Its mission is crystal clear: to shield a network from external threats like cunning hackers and malicious software.

Imagine the internet as a bustling city, and your browser as a messenger navigating its streets. When you type a URL like "google.com," the request your browser makes has to pass through the vigilant firewall. Picture the firewall as a checkpoint inspector, scrutinizing the incoming request to ensure it aligns with the network's security policies.

The firewall relies on two key types of security policies:

1. Origin-Destination Policies:

- This type permits or prohibits traffic based on where the request is coming from and where it's headed. Think of it like allowing or blocking certain neighborhoods from accessing specific parts of the city.

2. Traffic Type Policies:

- Here, the firewall allows or blocks traffic based on the nature of the request. It's akin to deciding which types of vehicles are allowed on certain roads, blocking the ones that might cause trouble.

As your incoming request approaches the firewall, it undergoes scrutiny against these policies, ensuring that only authorized traffic continues its journey.

HTTPS/SSL Encryption:

Now, let's explore the safety measures in place when your browser communicates with a server, especially one as prominent as Google.

1. HTTPS's Locked Box:

- HTTPS, the secure version of HTTP, acts like a locked box for transmitting data over the internet. When you type "google.com" into your browser, the request is sealed in this locked box before being sent to Google's server.

2. SSL/TLS as Special Codes:

- SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are the special codes used to lock and unlock this digital box. It's akin to having a secret code between you (the sender) and the server (the recipient) to ensure the safety of your communication.

Think of it as sending a secret message in a locked box, and only you and the recipient possess the key or code to unveil the contents. This encryption ensures that your data remains confidential during its journey from your browser to Google's server and back.

Load Balancer:

In the bustling city of internet traffic, a load balancer emerges as a traffic director, ensuring a smooth flow of visitors to various servers. For a giant like Google, handling billions of daily visitors necessitates the strategic use of a load balancer.

1. Even Traffic Distribution:

- The load balancer acts as a fair traffic cop, distributing incoming requests from browsers across Google's array of servers. This prevents overload on a single server and enhances the overall system capacity and reliability.

2. Behind-the-Scenes Decision Making:

- When your browser seeks to access "google.com," the load balancer steps in, receiving the request and deciding which server in the Google network should handle it. Think of it as the load balancer orchestrating traffic in a way that keeps everything running smoothly.

In essence, the firewall guards the gateway, HTTPS/SSL encrypts your communication, and the load balancer ensures a balanced flow of internet visitors, creating a secure and efficient online experience.

Web Server:

A web server, the unsung hero in the online symphony, is a software tasked with managing requests for web pages from clients, like a browser yearning to explore "google.com." Let's unravel the journey when you hit Enter.

1. Client Request to Web Server:

- When you request a web page, say "google.com," the client's request traverses through the load balancer and lands on Google's web server.

2. Web Server's Task:

- The web server diligently handles the request, crafting a response that typically includes the essential HTML, CSS, and JavaScript files constituting the web page.

3. Response Journey:

- The web server dispatches this response back to the load balancer, which, in turn, forwards it to your browser. The browser eagerly awaits this digital package to showcase the requested web page.

4. Client Presentation:

- Armed with HTML, CSS, and JavaScript, your browser takes the stage. It interprets the code, arranges text and images, and executes any interactive features scripted in JavaScript. The result? A visually appealing and functional web page laid out before you.

Application Server and Database:

Diving deeper into the realm of dynamic content, the application server assumes the spotlight. It doesn't just serve static web pages; it's the maestro orchestrating dynamic elements, especially evident in endeavors like a Google search.

1. Load Balancer's Role:

- As you submit a search query, the load balancer routes it to a web server. This server, recognizing the need for dynamic content, forwards the request to the application server.

2. Application Server's Task:

- The application server swings into action, generating dynamic content such as search results based on your query. For complex queries, it might even seek assistance from a database, extracting essential data.

3. Database Interaction:

- Imagine searching for a product on an e-commerce site. The application server might tap into the database to fetch detailed product information, enriching the dynamic content.

4. Response Journey:

- The application server sends the dynamic payload back to the web server, and subsequently, to your browser via the load balancer.

5. Client Presentation (Again):

- Your browser, ever the eager performer, processes this dynamic content alongside the static elements. The result is a comprehensive display of search results, combining text, images, and potentially interactive elements.

Displaying the Web Page:

1. Browser Processing:

- When your browser receives the complete response from the website server, it embarks on processing the HTML, CSS, and JavaScript files included in the payload.

2. Rendering the Web Page:

- It interprets HTML and CSS, places text and images in their designated spots, and executes any embedded JavaScript code.

3. User Interaction:

- With the webpage fully formed, you're now at the helm. Click links, type text, or interact with any features as your heart desires.

In conclusion, this journey from the client's request through web and application servers to the final webpage display is a harmonious interplay of technology, ensuring a seamless and engaging user experience. I trust this exploration has shed light on the intricate dance transpiring "behind the scenes" when you embark on a web-browsing adventure. Thank you for accompanying us on this journey.