Regex match (~, ~*) in Nginx - Step-by-Step Execution

Process Flow - Regex match (~, ~*)

Request URL Received

↓

Check location blocks

↓

Is location regex?

↓

Match with ~ or ~*

↓

If match found

↓

Use this location

↓

Process request

↓

If no match

↓

Try next location or default

Nginx checks request URLs against location blocks. If a location uses ~ or ~*, it tests the URL with regex (case-sensitive or insensitive). If matched, it uses that location.

Execution Sample

Nginx

location ~ ".*\.php$" {
    fastcgi_pass 127.0.0.1:9000;
}

location ~* ".*\.jpg$" {
    expires 30d;
}

Two location blocks: one matches URLs ending with .php (case-sensitive), the other matches URLs ending with .jpg (case-insensitive).

Process Table

Step	Request URL	Location Tested	Regex Type	Match Result	Action Taken
1	/index.php	location ~ ".*\.php$"	Case-sensitive (~)	Matches	Use this location, pass to fastcgi
2	/image.JPG	location ~ ".*\.php$"	Case-sensitive (~)	No match	Check next location
3	/image.JPG	location ~* ".*\.jpg$"	Case-insensitive (~*)	Matches	Use this location, set expires
4	/about.html	location ~ ".*\.php$"	Case-sensitive (~)	No match	Check next location
5	/about.html	location ~* ".*\.jpg$"	Case-insensitive (~*)	No match	No regex location matched, try other locations or default

💡 Request URL matched or no regex location matched, nginx proceeds accordingly.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5
Request URL		/index.php	/image.JPG	/image.JPG	/about.html	/about.html
Current Location Tested		location ~ ".*\.php$"	location ~ ".*\.php$"	location ~* ".*\.jpg$"	location ~ ".*\.php$"	location ~* ".*\.jpg$"
Match Result		Matches	No match	Matches	No match	No match
Action Taken		Use this location	Check next location	Use this location	Check next location	No regex location matched

Key Moments - 2 Insights

Why does location ~* ".*\.jpg$" match /image.JPG but location ~ ".*\.php$" does not match /image.JPG?

Because ~* means case-insensitive regex match, so .JPG matches .jpg ignoring case. The ~ operator is case-sensitive, so it does not match uppercase .JPG.

What happens if no regex location matches the request URL?

Nginx continues checking other non-regex locations or the default location block to handle the request, as shown in step 5 of the execution table.

Visual Quiz - 3 Questions

Look at the execution table, what is the match result for /index.php against location ~ ".*\.php$"?

A Matches

B No match

C Error

D Partial match

💡 Hint

Check Step 1 in the execution_table under 'Match Result' column.

At which step does nginx use a case-insensitive regex match?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Regex Type' column in the execution_table for step 3.

If the request URL was /photo.JPG, which location block would match it?

A location ~ ".*\.php$"

B location ~* ".*\.jpg$"

C No location matches

D Both locations match

💡 Hint

Refer to how ~* matches case-insensitively in the variable_tracker and execution_table.

Concept Snapshot

Nginx regex match uses ~ for case-sensitive and ~* for case-insensitive matching.
Syntax: location ~ /pattern/ { ... } or location ~* /pattern/ { ... }
Nginx tests request URLs against these regex locations in order.
If matched, nginx uses that location block to process the request.
If no regex matches, nginx tries other locations or defaults.

Full Transcript

When nginx receives a request URL, it checks location blocks to find a match. Locations using ~ perform case-sensitive regex matching, while ~* performs case-insensitive matching. For example, location ~ ".*\.php$" matches URLs ending with .php exactly, while location ~* ".*\.jpg$" matches .jpg endings ignoring case. Nginx tests each regex location in order. If a match is found, it uses that location block to handle the request. If no regex location matches, nginx tries other locations or the default. This process ensures flexible URL matching based on regex patterns.