Network

Question 1

What is the first thing that happens when you type a URL and press enter? And next?

Answer 1

The browser checks if the URL is valid and well-formed.

After that the browser tries to find the IP address in the DNS (domain name system) cache. If its not there, it looks for it in the DNS server using a recursive method.
When it finds it, browser then establishes TCP connection with the web server, sends the HTTP request to the server and the server sends back the http response so the browser can render the http content (html, javascript bundles and resources).

Question 2

What does DNS do in this process?

Answer 2

DNS translates the domain name (e.g., google.com) into an IP address.

Question 3

What happens after the IP address is resolved?

Answer 3

The browser establishes a TCP connection with the server using the resolved IP address.

Question 4

What is a TCP handshake?

Answer 4

It is a process of establishing a reliable connection between client and server (SYN, SYN-ACK, ACK).

Question 5

What protocol is used after TCP is established?

Answer 5

HTTP or HTTPS protocol is used to request data from the server.

Question 6

What happens during an HTTP request?

Answer 6

The browser sends a GET request for the specific resource (HTML, CSS, JS, etc.)

Question 7

What does the server do after receiving the HTTP request?

Answer 7

The server processes the request and sends back an HTTP response, usually starting with an HTML file.

Question 8

What happens when the HTML is received?

Answer 8

The browser parses the HTML, builds the DOM tree, and may make additional requests for CSS, JS, images, etc.

Question 9

What is the CSSOM?

Answer 9

CSSOM is the CSS Object Model; it represents the CSS styles parsed separately from the DOM.

Question 10

What is the Render Tree?

Answer 10

The Render Tree combines DOM and CSSOM to determine what is visible and how it should look.

Question 11

What happens during layout?

Answer 11

The browser calculates the position and size of each element on the page.

Question 12

What happens during painting?

Answer 12

The browser paints pixels on the screen based on the layout and styles.

Question 13

What is compositing?

Answer 13

The browser assembles layers (e.g., for animations) and sends them to the GPU for final rendering.

Question 14

What is the final step?

Answer 14

The page is displayed to the user; the browser continues to listen for further interactions.

Question 15

What role does the browser cache play?

Answer 15

It can speed up page load by storing previously fetched resources like images, scripts, and stylesheets.

Question 16

What is a Service Worker in this context?

Answer 16

It can intercept network requests and serve cached content to improve performance and offline access.

Question 17

What is HTTPS and why is it important here?

Answer 17

HTTPS encrypts data between the browser and server to ensure privacy and integrity.

Question 18

What is the role of cookies during this request?

Answer 18

Cookies may be sent automatically by the browser to provide session information to the server.

Question 19

How does the browser know how to handle a domain?

Answer 19

It checks the Same-Origin Policy to apply security rules to requests.

Question 20

What is a critical rendering path?

Answer 20

It is the sequence of steps the browser takes to convert HTML, CSS, and JS into pixels on the screen.

Question 21

What does URL stands for?

Answer 21

Uniform Resource Locator and consists of scheme (http or https), domain (example.com), path (/product), resource (/id)