What happens when you type https://www.google.com and hit ENTER.

This is something you have probably never thought about because of how seamless and fast it happens. When you type https://www.google.com and arrive at the results, it all happens so quickly that you do not even have time to think about how it occurs. Well, today I will break down what happens behind the scenes and why it happens so fast.

I believe you're familiar with what a Uniform Resource Locator(URL) is, these are a list of topics I will be discussing, this is what happens behind the scenes:

• DNS request
• TCP/IP connection
• Firewall
• HTTPS/SSL
• Load-balancer
• Web server
• Application server and database
• Rendering the page

DNS Request

Whenever you enter a domain name or website on your browser, the browser saves the DNS record in its cache. Thus, when you type a domain name like "google.com" on your web browser, it checks its cache for the most recent copy of the DNS record for that domain. If there is a recent copy of the DNS records for that domain, it will use the IP address in the cache to send a request to the server. This speeds up the process of resolving the domain name to an IP address because it avoids the need to send a request to the DNS server.

However, if the browser cache does not have a recent copy of the DNS record or if the DNS record has been updated since the last time it was cached, the browser sends a request to the DNS server to convert the domain name to an IP address. This is a complex process, so let's delve into the different stages involved.

DNS Lookup Process

Here's how the DNS lookup process works:

The browser sends a request to the local DNS resolver, which is often provided by the internet service provider (ISP). The local DNS resolver checks its cache for the most recent copy of the DNS record for the domain. If it has it, it sends the IP address back to the browser. If the local DNS resolver does not have the most recent copy of the DNS record, it sends a request to a root nameserver. The root nameserver replies with the address of a top-level domain (TLD) nameserver, such as .com

• The local DNS resolver sends a request to the TLD nameserver.
• The TLD nameserver responds with the address of the authoritative nameserver for the domain.
• The local DNS resolver sends a request to the authoritative nameserver.
• The authoritative nameserver responds with the IP address for the domain.
• The local DNS resolver sends the IP address back to the browser.
• The browser sends a request to the server at the IP address to retrieve the webpage.

This process may involve additional steps if the DNS record is not found at any of the nameservers or if the DNS record is set up to use a service such as DNS load balancing or content delivery networks (CDN).

The duration for which the DNS record is cached (known as the "TTL" or "Time To Live") is determined by the authoritative nameserver and can be customized by the domain owner.

TCP/IP connection

TCP (Transmission Control Protocol) and IP (Internet Protocol) are two of the main protocols that make up the internet. They work together to establish a connection between a client and a server and facilitate the transmission of data between them.

Here's what happens in greater detail:

• The browser uses IP to send a request to the server to establish a connection.
• The server receives the request and sends a message back acknowledging the request to establish a connection. This is known as the handshake procedure.
• Once the handshake is completed, the browser can use TCP to send a request for the webpage it wants to access (in this instance, the homepage of google.com). This request is made using TCP, which ensures that the request is sent reliably and in the correct sequence.
• The server receives the request and sends the HTML code for the homepage of google.com back to the browser. This response is also sent using TCP to ensure dependable transmission.
• The browser receives the HTML code and uses it to display the webpage on your screen. Any resources (such as images) that the webpage requires are also requested and received using TCP/IP.

Firewall

A firewall is a computer network security system that restricts internet traffic in to, out of, or within a private network. Its primary objective is to safeguard a network from external threats, such as hackers and malware.

When you type a URL like "google.com" into your browser, the request that your browser makes to Google's server passes through the firewall on its way. The firewall checks the incoming request to make sure it is allowed based on its security rules.

There are two main types of security rules that a firewall uses to check incoming requests:

1. Rules that allow or block traffic based on the source and destination of the request. For example, a firewall may be configured to block all traffic from certain countries or to allow only certain IP addresses to access the network.
2. Rules that allow or block traffic based on the type of traffic. For example, a firewall may be configured to block all traffic on certain ports (such as those used by malware) or to allow only certain types of traffic (such as HTTP or HTTPS).

If the incoming request meets the security rules set by the firewall in front of Google's server, it is allowed through, and the browser is able to access the website.

However, if the request does not meet the security rules, it is blocked, and the browser is unable to access the website.

HTTPS/SSL

HTTPS (Hypertext Transfer Protocol Secure) is a safe version of HTTP, which is used to transmit data on the internet. It encrypts the data sent between your browser and Google's server. SSL (Secure Socket Layer) and TLS (Transport Layer Security) are encryption protocols that ensure the safety of data transmitted over HTTPS.

When your browser connects to Google's server using HTTPS, it agrees with Google's server on the version of SSL/TLS to use and creates a secure, encrypted channel for data transmission.

Load-balancer

A load balancer is a device that distributes incoming network traffic across a group of servers or resources.

Its primary function is to ensure that the traffic is distributed evenly across the servers in order to avoid overloading any single server and to increase the overall capacity and reliability of the system.

A company like Google, which receives billions of website visitors a day, will need a lot of servers to serve all these users. Therefore, there will be a need for them to set up a load balancer to ensure that some of the servers are not overburdened while others are being underutilized.

In the case of a browser trying to access google.com, the load balancer would receive the incoming request from the browser and then forward it to one of the servers in the Google server network. The particular server chosen will depend on the type of load balancing algorithm implemented.

Web server

A web server is a computer program that is responsible for handling requests for web pages from clients (such as a browser trying to access google.com). When a client sends a request for a web page to a web server, the server processes the request and returns the appropriate response to the client.

This means that when trying to access google.com, Google's server will receive a request from the load balancer.

The web server would then process the request and generate a response, which would typically include the HTML, CSS, and JavaScript files that make up the web page.

The web server would then send this response back to the load balancer, which would forward it on to the browser. The browser would then use the HTML, CSS, and JavaScript files to render the web page for the user.

Application server and database

Unlike the web server, the application server handles dynamic content. When using "google.com", the application server will be responsible for generating the search results (which change based on the query you put into the search engine).

When you submit a search query to Google, the request is first sent to the load balancer, which forwards it to one of the web servers in the Google server network. The web server then sends the request to the application server, which processes the request and generates the search results.

Depending on the complexity of the search query, the application server may need to make a request to a database in order to retrieve the necessary data.

For example, if you are searching for a specific product on an e-commerce website, the application server may need to retrieve information about the product from a database.

Once the application server has obtained the necessary data, it sends it back to the web server, which includes it in the response that is sent back to the the browser. The browser then uses this information to display the search results to you.

Rendering the page

When a browser receives a response from a web server, it processes the HTML, CSS, and JavaScript files that are included in the response in order to render the web page.

The rendering process involves interpreting the HTML and CSS code, rendering any images or other media that are included on the page, and executing any JavaScript code that is present on the page.

In your case, your browser would receive the response from the web server, which includes the HTML, CSS, and JavaScript files that make up the Google web page.

The browser would then use these files to render the page and display it to you. This process typically involves the following:

• displaying the text and images on the page in the appropriate positions
• formatting the text and layout according to the CSS styles
• executing any JavaScript code that is present on the page

Once the page has been fully rendered, you can now interact with it by clicking links, entering text, or interacting with other elements on the page.

Conclusion

In conclusion, I believe this post has given you a better understanding of what happens “behind the scenes” when you type https://www.google.com into your browser and press Enter. Thank you.