# What Happens When You Type a URL and Press Enter — Step by Step

Source: https://skills101.in/learn/computer-networks/what-happens-when-you-type-a-url — Skills101 free tutorial (Computer Networks). Updated 2026-11-09.

"What happens when you type **skills101.in** into the browser and press Enter?" is asked in almost every networking and web interview. It tests whether you can connect everything you've learned.

![Seven steps: DNS lookup, TCP connection, TLS handshake, HTTP request, server work (load balancer, app, database), HTTP response, and rendering](https://skills101.in/learn-img/computer-networks/url-journey.svg)

## The 7 steps

### 1. Understand the input and find the IP (DNS)

- The browser decides it's a URL (not a search), and adds `https://`.
- It checks the **browser cache, OS cache and hosts file**; if needed, asks the **DNS resolver**, which walks root → `.in` → skills101's name server and returns an IP like 203.0.113.7.

### 2. Open a TCP connection

- The browser connects to that IP on **port 443** with the **three-way handshake** (SYN, SYN-ACK, ACK).
- Under the hood: the OS finds the **gateway (router)** using its routing table, uses **ARP** to get the router's MAC address, and the packet hops router to router across the internet.

### 3. TLS handshake (because it's HTTPS)

- The server sends its **certificate**; the browser checks it's valid for skills101.in and signed by a trusted CA.
- They agree on **session keys**. From now on, everything is encrypted.

### 4. Send the HTTP request

```text
GET / HTTP/2
Host: skills101.in
Cookie: session=…
Accept: text/html
```

### 5. The server side

- A **CDN** may answer static files from a nearby city.
- Otherwise a **load balancer** (e.g. nginx) forwards the request to an **application server**.
- The app checks the session cookie, maybe reads from a **cache** (Redis) or the **database**, and builds the HTML.

### 6. The response

```text
HTTP/2 200 OK
Content-Type: text/html
Cache-Control: max-age=60
```

followed by the HTML. The browser then requests CSS, JavaScript, images and fonts (often in parallel, often from the CDN).

### 7. Render the page

- Parse HTML → **DOM**; parse CSS → **CSSOM**; combine → **render tree**.
- **Layout** (positions and sizes) → **paint** pixels → JavaScript runs and makes it interactive.

## How to answer in an interview

1. Start with the **7-step outline** (30 seconds).
2. Ask: "Which part would you like me to go deeper into?"
3. Go deep where you're strong: DNS caching, the TLS handshake, load balancing, or browser rendering.

## Extra details that impress

- **HTTP keep-alive / HTTP/2** reuse one connection for many requests.
- **HSTS** tells the browser to always use HTTPS for a site.
- **Caching** at every level: browser, DNS, CDN, server, database.
- **HTTP/3** runs over **QUIC (UDP)** to cut handshake delay.

## Common mistakes

- Skipping DNS or the TLS handshake.
- Saying "the server sends the website" without mentioning the request/response structure.
- Going too deep in one area before giving the full outline.

## Quick recap

- DNS → TCP → TLS → HTTP request → server (CDN, load balancer, app, cache, DB) → response → render.
- Give the outline first, then go deep where asked.


Practice quiz and free certificate: https://skills101.in/learn/computer-networks/what-happens-when-you-type-a-url