Next time when someone asks you, What happens when you enter google.com in your browser?

🧩 Step 0: The Goal

Your browser needs to find the IP address of google.com so it can connect to the web server.
DNS is the system that helps it find that IP.

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⚙️ Step 1: Browser & OS Local Cache

When you type google.com:

1. Your browser first checks its own cache (recently visited sites).

2. If not found, your operating system checks its local DNS cache (for example, your /etc/hosts file on Linux or Windows DNS resolver cache).

If found → done (no network query needed).
If not found → move to the next level.

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⚙️ Step 2: The Resolver (Usually Your ISP or a Custom One)

Your computer sends the DNS query (like “What is the IP of google.com?”) to a recursive resolver.
This is typically:

• your ISP’s DNS resolver, or

• a public resolver like 8.8.8.8 (Google DNS) or 1.1.1.1 (Cloudflare DNS).

This resolver’s job is to find the answer for you — it does all the hard work by asking other DNS servers in the hierarchy.

If it already has the answer cached → returns it immediately.

If not cached → it starts the DNS resolution process below.

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⚙️ Step 3: Root DNS Servers

The resolver sends a query to a Root DNS Server:

“Hey, where can I find info about .com domains?”

Root servers don’t know about individual domains like google.com,
but they do know where the Top-Level Domain (TLD) servers are.

So the root server replies:

“I don’t know google.com, but here’s a list of .com TLD name servers.”

It returns a referral to the .com TLD servers.

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⚙️ Step 4: TLD (Top-Level Domain) Name Servers

Now, the resolver contacts one of the .com TLD servers:

“Hey, I need info about google.com — who’s the authoritative server for it?”

The TLD server replies:

“The authoritative name servers for google.com are ns1.google.com, ns2.google.com, etc.”

This is another referral — now we know where the actual zone for google.com is managed.

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⚙️ Step 5: Authoritative DNS Server

Finally, the resolver asks Google’s authoritative name server:

“What is the IP address (A record) for google.com?”

This server owns the actual DNS records for google.com.
It replies with something like:

“google.com → 142.250.190.14”

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⚙️ Step 6: Returning the Result

The recursive resolver now:

• Stores this result in its cache for some time (defined by the TTL).

• Sends the IP address back to your computer.

Your OS also caches it for a while.
Then your browser uses that IP to make an HTTP(S) request to https://142.250.190.14.

Short Hierarchy:

Question :
Why Caching Matters and what happens when cached?

Because of all following steps below, caching is critical for performance:

• Browser and OS caches: avoid repeated lookups.

• Resolver caches: millions of users share results.

• Each record has a TTL (time-to-live) after which it expires and must be re-fetched.