How does Browser Opens any Website

aditya goel
3 min readJan 21, 2023

Question:- What happens when someone types-in some URL into the Browser ?

Answer → Following are the steps being followed, whenever someone types-in some URL into the Browser :-

Step 1.) Client enters the URL into the Browser.

Step 2.) Browser needs to know, how to reach to the Server (In this case → This is done using the process of DNS-LookUp. Basically, objective here is to find the IP-Address of the server.

Step 3.) Browser then establishes the TCP-connection with the Server, using the IP-address it got.

Step 4.) Browser now sends HTTP request to the Server, over the established TCP-connection.

Step 5.) Server processes the request & sends back the response.

Step 6.) Browser now reads the response & finally renders the content.

Question:- What are various components of the URL ?

Question:- Explain a bit about the process of DNS ?

  • DNS stands for Domain Name System. DNS is Phonebook of Internet.
  • DNS helps to translate the domain name to the IP-Address of the server, so that Browser can know the resources.

Question:- Explain the process of DNS-LookUp ?

Answer → This process is an elaborate and elegant process. DNS information is heavily cached at various places :-

  • First, Browser checks for this information from its own caches for a short period of time.
  • Next step, if the DNS mapping is not being found, then it checks with the Machine’s Operating-System which also caches this information for a short period of time.
  • Next, if the DNS mapping is still not being found from the OS’s cache, then Browser makes a query out to the Internet to a DNS-Resolver. This further sends out the chain of requests, until the DNS-mapping is being found. This step involves many servers in the DNS Infrastructure.

Finally, the Browser has the IP-address of the server. This has been shown above in step-2nd of image above.

Question:- Explain how does the TCP Connection established ?

Answer → This is again an detailed and complex process :-

  • There is a handshake involved in establishing the process of TCP-Connection. It takes several network-round-trips , in order for this process to complete.
  • In order to make this process faster, modern browsers uses something called as Keep-Alive-Connection, to try to reuse & establish TCP connection to the Server as much as possible.
  • If the connection to be established is HTTPS, then the process to establish connection is even more complex. It requires SSL-TLS-Handshake, to establish encrypted connection between the Browser & Server.
  • This Handshake is expensive and therefore the Browsers uses techniques like SSL-Redemption, to try to lower the cost.

Finally, the Browser is able to establish a TCP-Connection with the Server. This has been shown above in step-3rd of image above.

That’s all in this blog. If you liked reading it, do clap on it. We shall see you in next document..



aditya goel

Software Engineer for Big Data distributed systems