server_name directive in Nginx - Step-by-Step Execution

Process Flow - server_name directive

Start: HTTP request arrives

↓

Check Host header

↓

Match server_name directive?

No→Default server handles request

Yes↓

Route request to matching server block

↓

Process request with matched server config

↓

Send response back to client

The server_name directive matches the Host header of incoming requests to route them to the correct server block.

Execution Sample

Nginx

server {
    listen 80;
    server_name example.com www.example.com;
    root /var/www/example;
}

This config routes requests with Host 'example.com' or 'www.example.com' to this server block.

Process Table

Step	Incoming Host header	server_name match?	Action	Result
1	example.com	Yes	Route to this server block	Serve content from /var/www/example
2	www.example.com	Yes	Route to this server block	Serve content from /var/www/example
3	test.com	No	Check other server blocks or default	Request handled by default server
4	example.net	No	Check other server blocks or default	Request handled by default server

💡 Request is routed to the server block whose server_name matches the Host header; otherwise default server handles it.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
Host header	none	example.com	www.example.com	test.com	example.net
Matched server block	none	example.com block	example.com block	none	none

Key Moments - 2 Insights

Why does a request with Host 'test.com' not match the server_name?

Because 'test.com' is not listed in the server_name directive (see execution_table row 3), so nginx routes it to the default server.

Can server_name match multiple names?

Yes, server_name can list multiple names separated by spaces (see execution_sample), so requests with any of those names match this server block.

Visual Quiz - 3 Questions

Look at the execution table, which Host header matches the server_name directive?

A example.com

B test.com

C example.net

D none of the above

💡 Hint

Check the 'server_name match?' column in execution_table rows 1-4.

At which step does nginx route the request to the default server?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for 'No' in 'server_name match?' and 'Request handled by default server' in execution_table.

If we add 'test.com' to server_name, what changes in the execution table?

A Step 1 would no longer match

B Step 3 would show a match and route to this server block

C Step 4 would match instead of default

D No changes would occur

💡 Hint

Adding 'test.com' to server_name means requests with Host 'test.com' match this block (see execution_table row 3).

Concept Snapshot

server_name directive:
- Defines domain names nginx listens for
- Matches Host header in HTTP requests
- Multiple names separated by spaces
- If no match, default server handles request
- Used to route requests to correct server block

Full Transcript

The server_name directive in nginx tells the server which domain names it should respond to. When a request arrives, nginx looks at the Host header and compares it to the names listed in server_name. If it finds a match, it sends the request to that server block. If not, the default server handles the request. You can list multiple names in server_name separated by spaces to match different domains. This helps nginx know which website content to serve based on the domain the user typed.