What happen when you click the URL?
This is a very common interview question! I got the question twice and guess what? I f*ked up twice!
When you wrote URL and click Enter, you’ll see the website that you want to go opened in milliseconds, but what’s going on in the background?
Simply explain is;
I write the URL on browser and click Enter, browser takes it and gets an IP address using DNS, opens TCP connection via IP with HTTP protocol -or HTTPs if the website has an SSL. Sends information to the Physical layer, it sends information bottom to up, and I see the website.
- Application layer used for the process of mine,
- HTTP/s transmits the information to Network layer, now there’re two addresses for client and server.
- Network layer sends to Data Link layer to obtain MAC address as the physical address.
- Finally reached the Physical layer to obtain required data, to reach the server. There’re only bits on this layer.
- When the data obtained, packages send to me as a client, from Physical layer to Application layer, bottom to up. And here it is! I see the website response.
Uniform Resource Locators as URLs
URL is locator of the resource that we want to access and retrieve the data at the location. URL contains all the information of that browser needs.
Layers
Open Systems Interconnection (OSI) model is important to understand what’s happening on backside.
It’s a standart for the communicate between computer systems. There is 7 layers in this model. Simply, those layers communicate, transfer informations and makes abstraction between them while doing these things and importantly helps us to see and use websites. You can find more here.
- Thanks to Scott Hanselman for the video to definitive explain https://www.youtube.com/watch?v=vvpCnjyjTuU
- And here I found of Maneesha Wijesinghe article for the deep dive explanation https://medium.com/@maneesha.wijesinghe1/what-happens-when-you-type-an-url-in-the-browser-and-press-enter-bb0aa2449c1a
And other two explanations you can find below;
