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What Happens When You Open a Website? A Simple Breakdown

What Happens When You Open a Website? A Simple Breakdown

Pravin Jadhav's photo
Pravin Jadhav

Have you ever wondered what happens behind the scenes when you type something like amazon.in into your browser and hit Enter? It feels like magic—one second you’re staring at a blank screen, and the next, you’re browsing through products. But under the hood, a lot is going on. Let me break it down for you in simple terms, step by step.

1. You Type the URL and Hit Enter

Imagine you’re sending a letter to a friend. First, you need to write their address on the envelope. When you type amazon.in in your browser, you’re essentially writing the address of the website you want to visit.

  • Browser Check: The browser checks if the address is valid. If you forget to add https://, it’ll assume you meant https:// (the secure version).

2. DNS Lookup: Finding the Right House

Now that you have the address, you need to find the exact location. This is where DNS (Domain Name System) comes in. Think of DNS as a phonebook for the internet.

  • Browser Cache: First, the browser checks its own memory to see if it already knows the IP address for amazon.in.

  • OS Cache: If not, it asks your computer’s operating system.

  • DNS Server: If it’s still not found, the browser contacts a DNS server (like Google’s 8.8.8.8) to get the IP address (e.g., 54.239.33.123).

This is like looking up your friend’s house on a map so you know where to send the letter.

3. TCP Handshake: Knocking on the Door

Now that you have the IP address, your browser needs to establish a connection with Amazon’s server. This is done through a TCP handshake, which is like knocking on the door and introducing yourself.

  • SYN: Your browser says, “Hey, I want to talk!”

  • SYN-ACK: The server replies, “Sure, let’s talk!”

  • ACK: Your browser says, “Great, let’s go!”

This three-step process ensures a reliable connection.

4. TLS Handshake: Securing the Conversation

If you’re using https:// (which you should!), your browser and the server need to agree on how to encrypt the conversation. This is called the TLS handshake.

  • Encryption Setup: They agree on a secret code to keep the conversation private.

  • Certificate Check: Your browser checks Amazon’s ID (SSL/TLS certificate) to make sure it’s really Amazon and not an imposter.

Think of this as locking the door so no one else can eavesdrop.

5. HTTP Request: Asking for the Page

Now that the connection is secure, your browser sends an HTTP request to the server. It’s like saying, “Hey, can I have the homepage of Amazon?”

  • Method: The request type is usually GET (meaning “give me this page”).

  • Headers: It includes extra info like your browser type, language preferences, and cookies (if you’ve visited before).

6. Server Response: Delivering the Goods

Amazon’s server processes your request and sends back a response. This includes:

  • Status Code: Like a thumbs-up (200 OK) or a “page not found” (404).

  • Headers: Metadata about the response (e.g., content type, caching rules).

  • Body: The actual content of the page (HTML, CSS, JavaScript).

This is like your friend sending back a package with everything you asked for.

7. Rendering: Building the Page

Now comes the fun part—your browser takes the response and builds the page you see on your screen.

  • HTML Parsing: The browser reads the HTML and creates a DOM tree (a map of the page’s structure).

  • CSS Parsing: It fetches and applies styles to the DOM, creating a CSSOM.

  • JavaScript Execution: Any JavaScript is run, which can modify the DOM or CSSOM.

  • Render Tree: The browser combines the DOM and CSSOM to create a render tree (what you’ll actually see).

  • Layout and Painting: The browser calculates where everything goes and paints it on the screen.

This is like assembling a piece of furniture using the instructions (HTML), paint (CSS), and tools (JavaScript) provided.

8. Loading Additional Resources

The page might need more stuff, like images, videos, or fonts. Your browser downloads these in the background.

  • CDN: Many websites use Content Delivery Networks (CDNs) to serve these resources from servers closer to you, making things faster.

9. Caching: Saving for Later

To speed things up next time, your browser saves some of the resources (like images or stylesheets) in its cache. This is like keeping a copy of your friend’s letter so you don’t have to ask for it again.

10. User Interaction: Keeping the Conversation Going

Once the page is loaded, your browser stays connected to handle your actions—like clicking a button, filling out a form, or navigating to another page. Each action might trigger new requests to the server.

Simplified Analogy

Imagine you’re ordering food from a restaurant:

  1. URL Entry: You decide what you want to eat (e.g., pizza from “Pizza Place”).

  2. DNS Lookup: You look up the restaurant’s phone number.

  3. TCP Handshake: You call the restaurant and say, “Hello, can I order?”

  4. TLS Handshake: You agree on a secret code to keep your order private.

  5. HTTP Request: You tell the restaurant what you want (e.g., “One large pizza, please”).

  6. Server Response: The restaurant prepares your order and sends it to you.

  7. Rendering: You unpack the pizza, arrange it on a plate, and get ready to eat.

  8. Additional Resources: You might also get sides like drinks or dipping sauces.

  9. Caching: You save the restaurant’s number for next time.

  10. User Interaction: You enjoy your pizza and maybe order dessert later.

Optimizations in Real Life

Big websites like Amazon use tricks to make this process faster:

  • CDNs: Deliver resources from servers near you.

  • Lazy Loading: Only load images when you scroll to them.

  • Minification: Shrink files (like JavaScript and CSS) to make them smaller.

  • Caching: Save reusable resources so they don’t need to be downloaded again.

Final Thoughts

The next time you open a website, remember that it’s not magic—it’s a carefully orchestrated dance between your browser and the server. From DNS lookups to rendering, every step plays a crucial role in delivering the page to your screen.

If you found this breakdown helpful, let me know in the comments! And if you’re curious about any specific step, I’d be happy to dive deeper. 😊

P.S. If you’re a visual learner, here’s a quick diagram to summarize the process:

Browser: URL → DNS Lookup → TCP/TLS Handshake → HTTP Request
Server: Process Request → Send Response (HTML, CSS, JS)
Browser: Parse → Render → Load Resources → Display Page

Happy browsing! 🚀