How DNS, HTTP and TLS Work, in Simple Terms

You may have heard these terms before: TNS. HTTP. DNS.

Whenever you visit a website, several things happen behind the scenes before the page appears on your screen. For example, you type a URL like https://example.com, press Enter, and the website loads. But how does your browser know where to find the website? How does it communicate with the server? And how is your connection secured?

Let's break it down.

1. DNS: Finding the Server

DNS stands for Domain Name System. It helps translate domain names into IP addresses. Computers communicate with one another using IP addresses, but remembering an IP address for every website would be difficult. DNS allows us to use domain names instead.

For example:

example.com → 93.184.216.34

When you visit a website, your computer needs to find the IP address associated with its domain name. It checks available DNS information, often through a DNS resolver, which may retrieve the answer from its cache or query other DNS servers.

Once the IP address is available, your browser knows where to send its connection request.

We can think of DNS as the phonebook of the internet. You know the person's name, but you need their number to contact them.

2. HTTP: Communicating With the Server

HTTP stands for Hypertext Transfer Protocol. This defines how a browser and a web server communicate. The browser sends requests, and the server responds.

For example, when you visit a website, your browser may send a request like this:

GET / HTTP/1.1
Host: example.com

This tells the server that the browser wants to retrieve the homepage.

The server may respond with:

HTTP/1.1 200 OK
Content-Type: text/html

The 200 OK status means the request was successful. The response can then contain the HTML document that your browser displays.

There are different HTTP methods:

• GET – Retrieve information.
• POST – Send data to the server.
• PUT – Replace or update a resource.
• DELETE – Delete a resource.

HTTP also has status codes such as 404 Not Found, 500 Internal Server Error, and 403 Forbidden.

Think of HTTP as the language your browser and server use to communicate.

3. TLS: Securing the Connection

TLS stands for Transport Layer Security. It protects communication between your browser and the server by encrypting data, helping prevent unauthorized parties from reading or modifying it while it travels across the network. This is why you see HTTPS instead of HTTP when visiting secure websites.

HTTPS is simply HTTP communication protected by TLS.

When a browser connects to a website using HTTPS, a TLS handshake takes place. During this process:

• The server presents its TLS certificate.
• The browser verifies that the certificate is valid for the domain and trusted.
• Both sides establish the cryptographic keys used to protect the connection.
• Secure HTTP communication begins.

This means sensitive information such as passwords, authentication tokens, and payment details can travel securely between the browser and the server.

Think of TLS as a secure, private channel between your browser and the server.

4. How They Work Together

Let's put everything together.

When you visit:

https://example.com

The process looks something like this:

1. Your browser identifies example.com as the domain it needs to reach.
2. DNS helps your browser obtain the server's IP address.
3. Your browser connects to the server.
4. TLS establishes a secure connection and verifies the server's identity.
5. Your browser sends an HTTP request over that secure connection.
6. The server processes the request and sends an HTTP response.
7. Your browser receives the response and displays the website.

You enter a URL
      |
      v
     DNS
Find the server IP
      |
      v
     TLS
Establish secure connection
      |
      v
     HTTP
Send request and receive response
      |
      v
 Website loads

5. Why This Matters in DevOps

Understanding DNS, HTTP, and TLS is important because many production issues involve one or more of them.

For example:

• A website pointing to the wrong IP address? Check DNS records.
• A website returning 502 Bad Gateway? Check the web server or reverse proxy and its upstream application.
• A website showing a certificate warning? Check its TLS certificate and configuration.
• An application working on HTTP but failing on HTTPS? Investigate TLS, reverse proxy, and application configuration.

These concepts also help when configuring domain names, Nginx, load balancers, cloud infrastructure, and application deployments.

Before troubleshooting a website, we should understand how a request gets from a user's browser to your server and back again.