What is website URL

#javascript #node #programming #beginners

Website url 🔗

URL (Uniform Resource Locator) is the so-called address of the desired resource on the internet that consists of multiple components/parts.

Let's take a look at the following URL
https://admin:pass@a.b.example.com:888/users/index.php?q=bob&role=2#info
This URL consist of the following components:

Scheme https://
Authority admin:pass@
Host a.b.example.com
Port 888
Path users/index.php
Query q=bob&role=2
Hash #info

Scheme component
Alternative naming: Protocol
Required: Yes
Example: https://

The scheme specifies which application will be used by a web server (app on Windows/i0S/Android) to open a URL.

For example, opening a URL with the scheme mailto:// will open your webmail application.

Common examples: https://, http:// , ftp://, mailto://, file://
Custom app examples: facetime://, slack://, steam://
Browser specific examples: about://, chrome://
Additional browser examples: data://, javascript://

Authority component
Alternative naming: HTTP authentication, credentials, authorization
Required: No
Example: admin:pass@

Basic authorization to a web/app resource indicated by @ (at) sign.
Login admin is separated from password pass using : (colon) sign
In some cases password is optional (e.g. https://admin@example.com)

Host component
Alternative naming: Hostname
Required: Yes
Example: a.b.example.com

The Host consists of multiple domain names separated by . (dot) sign.
Domain name with level > 2 is called sub-domain

a - 4th level domain (sub-domain)
b - 3rd level domain (sub-domain).
example - 2nd level domain (domain name)
com - top/1st level domain (TLD)
The host can be an IP address in IPv4 (e.g. 193.184.216.34)
or IPv6 (e.g. [2a00:1450:400e:80a::200e]) format

Port component
Required: Yes
Example: 888

The port component indicates which server we are referring to on the target host

The : (colon) sign indicates port component usage. 888 is the port number

The server can accept connections on multiple ports. E.g. port numbers 80 and 443 can be used by a single server:

80 - port number is used for basic web connection
443 - port number is used for secure (TLS/SSL) web connection
The port :443 or :80 is omitted when a web page has https:// or http:// scheme

Path component
Required: No
Example: /users/index.php

Usually the Path component indicates a path to target file on a server

/ - the root path/folder. Let's imagine it is called htdocs
users - folder named users inside of htdocs folder
/index.php - file named index.php inside of users folder
In some cases, the Path component can use custom mapping/scheme/rewrite rule. The path segments can be linked to a function/method in different files on a server:

/users/list - function list in users.php file.
show list of all users

/users/1/read - function read with argument ID in users.php file.
show info of user with ID = 1

/users/images - function users in image-collection.php file.
show images of all users

Query component
Alternative naming: Query string, Search string
Required: No
Example: ?q=bob&role=2

The Query component always starts with a ? (question) sign.
It consists of key-value pairs. The value is assigned to a key using the = (equals) sign.

Key-value pairs are separated using & (ampersand) sign.

? - starting symbol that indicates presence of Query component
q - the first key
= - the sign, that assigns first value to a first key
bob - the first value
& - the key and value pair separator
role - the second key
= - the sign, that assigns second value to a second key
2 - the second value
Example of logic behind this query: get all users named bob with role ID 2

Hash component
Alternative naming: Anchor
Required: No
Example: #info

Usually used by client-side scripting language named Javascript
By default - the browser will make a focus on an element with id after # (hash) sign. In our case, the focus will be made on an element with ID info