What happens when you type a URL in the browser and press enter?

Maneesa Wijesinghe-Nelken
7 min readApr 26, 2017

If you are in any technical profession, I am sure someone at some point has asked you this question. Whether you are an engineer, developer, marketer, or even in sales, it is always good to have a basic understanding of what is going on behind our browsers and how information is transferred to our computers via the internet.

Let’s imagine that you want to access maps.google.com to check the exact time it would take for you to get to your dinner reservation from work.

1. You type maps.google.com into the address bar of your browser.

2. The browser checks the cache for a DNS record to find the corresponding IP address of maps.google.com.

DNS(Domain Name System) is a database that maintains the name of the website (URL) and the particular IP address it links to. Every single URL on the internet has a unique IP address assigned to it. The IP address belongs to the computer which hosts the server of the website we are requesting to access. For example, www.google.com has an IP address of 209.85.227.104. So if you’d like, you can reach www.google.com by typing http://209.85.227.104 on your browser. DNS is a list of URLs, and their IP addresses, like how a phone book is a list of names and their corresponding phone numbers.

The primary purpose of DNS is human-friendly navigation. You can easily access a website by typing the correct IP address for it on your browser, but imagine having to remember different sets of numbers for all the sites we regularly access? Therefore, it is easier to remember the name of the website using a URL and let DNS do the work for us by mapping it to the correct IP.

To find the DNS record, the browser checks four caches.

● First, it checks the browser cache. The browser maintains a repository of DNS records for a fixed duration for websites you have previously visited. So, it is the first place to run a DNS query.

● Second, the browser checks the OS cache. If it is not in the browser cache, the browser will make a system call (i.e., gethostname on Windows) to your underlying computer OS to fetch the record…