What Is A URL?

Date First Published: 29th March 2022

Topic: Computer Networking

Topic: Network Identifiers

Computer Terms & Definitions

Difficulty Level: 2/10

Learn more about what a URL is in this article.

Short for a uniform resource locator, a URL is the web address of a webpage or file on the internet. It uniquely identifies the location of a webpage on the World Wide Web. For example, the web address (URL) of this article is: https://computerhelp4all.com/articles/what-is-a-url.html. URLs can be viewed in web browsers, by the web address, and are usually located towards the top of the screen.

In addition, typing the URL of a website is a quicker way to visit a website. For example, it would be much quicker to just type 'youtube.com' into the address bar of the web browser rather than using Google, typing 'YouTube' and then finding a search result that links to Youtube.

Properties

HTTP

Short for hypertext transfer protocol, HTTP is how devices communicate over the World Wide Web and request webpages. HTTP or HTTPS is always the first part of a URL. Most webpages start with HTTPS as it is the secure version of HTTP that encrypts sent data with SSL/TLS.

WWW

Short for World Wide Web, WWW is an optional property in a URL. Some websites still start with 'WWW', especially if they have been around for a long period of time. WWW is technically redundant and unnecessary in a URL and can be dropped, since every webpage on the internet is on the World Wide Web. However, some websites may require people to type 'www' before the domain name and missing 'www' will redirect them to the URL with 'www'.

Domain name or IP address

The domain name is the unique address of the website that is usually the name of the company or website. For example, the domain name of Youtube is 'youtube.com'. DNS is responsible for storing and translating the domain name of the website to an IP address, so when a webpage is visited, the IP address is actually being visited. Domain names are just easier for people to remember. Longer domain names, such as mysite.wordpress.com are known as subdomains since they are part of the primary domain name, 'wordpress.com'. The extension of the domain name, such as '.com', '.net', and '.org' is known as the TLD.

Some websites do not have domain names. Instead, people visit them by typing the IP address, a string of four unique numbers that uniquely identifies a device on the network, such as '123.123.123.123. When a website is being hosted by a web server, it will be assigned a unique IP address. It might be the IP address of the network provided by the ISP. These are much harder for people to remember and look unreliable. When visiting a website by IP address, the URL will be: http://123.123.123.123.

Location of the webpage

In order to find webpages on a website, its address will need to be typed. In most cases, it is unnecessary for users to manually type web addresses, since clicking on links to pages on a webpage will automatically take them to a page with that URL. Every page of a website has a unique URL. It consists of the domain name or IP address with the name of the webpage, such as 'http://example.com/example-webpage.html'. It is possible to name a webpage anything. Typing a URL to a webpage that does not exist will return a 404 error, meaning that the page cannot be found.

Most websites use directories (folders) for organising files. For example, a specific folder may be allocated for CSS files. When the file is in a directory, a forwards slash is used (e.g. http://example.com/css/style.css). The file extension (e.g. .html) identifies the type of file. For example, .js, would indicate that the file is a JavaScript file. Each file extension performs a specific function.

Network Port

In some cases, a URL may contain the network port, a unique 16-bit unsigned number that identifies a specific process or type of network service. An example of this is localhost. The default port for localhost is :80. However, the port of localhost can be changed to an unused port, usually 8080. In that case, users would have to visit 'localhost:8080'. Localhost refers to one's own computer, as suggested in the two words 'local' and 'host' as the word 'locally' means one's own computer. Localhost is often used when having a virtual server on one's server. The webpages can be seen on one's own computer.

Note:

It is not possible to add a port in DNS, since DNS only works with domain names and IP addresses. You will never see a public domain name with a port number at the end, such as 'example.com:80'. Port numbers can only be specified in localhost.

Disallowed characters

Some characters in URLs are not allowed. Spaces are not allowed, such as (e.g. http://example.com/a rticle.html). URLs can only contain alphanumeric characters and these characters: ()$-_+*'. Any other characters are disallowed.

Complex URLs

Some URLs are more complex, such as URLs that appear when a query is typed into a search engine. For example, the URL of searching on Google 'what is my IP address' is 'https://www.google.com/search?q=what+is+my+ip+address'. The 'q' in the URL means query. These URLs contain dynamic parameters.

URL Prefixes

Prefixes other than HTTP exist, including:

• FTP - Files available for download through the FTP protocol. These are used for transferring files from one device to another over the internet.
• Mailto - Provides a direct link to an email address. When clicked on, it will open in an email application with the address of the sender in the message.
• File - Technically not a URL as it is not accessible over the internet. Used for specifying the path for a file, usually HTML on a local computer.
• News - Used for viewing discussions located within a certain newsgroup.
• Telnet - A protocol that enables remote files to be requested from devices and communication with a web server or remote device using Unix commands.