What is Uniform Resource Locator (URL)

A web browser with a url bar and a globe in the background

An internet user’s experience of the web is facilitated by a Uniform Resource Locator (URL). URLs provide a unique address for every web page, allowing users to access the resource by clicking a link or entering the URL in their browser’s address bar.

Understanding the Basics of URLs

Before diving into the specifics of URLs, let’s first understand what a URL is and how it works. A URL, or Uniform Resource Locator, is a web address that identifies the location of a resource on the Internet. URLs are used to access web pages, files, images, videos, and other types of online content.

When you type in a URL or click on a link, your browser sends a request to the server identified by the URL. The server then retrieves the requested resource and sends it back to your browser, which displays the resource on your device.

Definition of a URL

At its most basic level, a URL consists of two parts: the protocol identifier and the resource identifier. The protocol identifier defines the communication protocol used to access the resource, while the resource identifier identifies the name or location of the resource.

For example, in the URL “https://www.example.com/index.html”, “https://” is the protocol identifier and “www.example.com/index.html” is the resource identifier.

Components of a URL

A URL typically contains several components, including:

  • Protocol – specifies the method that will be used to transfer the data. The most common protocols are HTTP and HTTPS, but there are others such as FTP and SMTP.
  • Domain name – identifies the website that hosts the resource. The domain name can be further broken down into subdomains, such as “www” in “www.example.com”.
  • Path – identifies the specific location of the resource on the server. This can be a file path, such as “/images/picture.jpg”, or a directory path, such as “/blog/2021/”.
  • Parameters – provide additional information about the request, such as search terms or user preferences. Parameters are separated from the rest of the URL by a question mark “?” and are in the form of key-value pairs, such as “?q=URLs”.

How URLs Work

As mentioned earlier, when a user enters a URL into their browser or clicks on a link, the browser sends a request to the server identified by the URL. The server then retrieves the requested resource and sends it back to the user’s browser, which displays the resource on the user’s device.

But URLs can also include additional parameters that specify how the resource should be handled. For example, a parameter could be used to tell the server to return a specific version of the resource, or to include additional information in the response.

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Understanding the basics of URLs is essential for anyone who uses the Internet, whether you’re a casual user or a web developer. By knowing how URLs work and what each component does, you can navigate the web more efficiently and effectively.

The Evolution of URLs

Early Internet and the Need for URLs

The development of URLs can be traced back to the early days of the internet when it was primarily used for research and academic purposes. At that time, accessing online resources required users to memorize the IP addresses of the servers hosting the resources.

However, as the internet grew and more resources became available, it became increasingly difficult for users to keep track of the IP addresses of all the resources they wanted to access. This led to the need for a system that could assign unique names to resources, making them easier to identify and access.

Recognizing the limitations of using IP addresses to access online resources, a group of researchers developed a system to create unique names that could be used to identify resources. This system came to be known as URLs.

URLs, or Uniform Resource Locators, are the addresses used to identify online resources, such as web pages, images, and videos. They consist of several parts, including the protocol, domain name, and path, and are used by web browsers to access and display online content.

Development of the URL Standard

As the internet grew, the need for a standardized method of creating and using URLs became apparent. In 1994, the World Wide Web Consortium (W3C) created a standard for URLs, which provided guidelines for their creation and use.

The standardization of URLs helped to ensure that they could be used consistently across different platforms and devices. This made it easier for users to access online resources and for developers to create websites and applications that could be accessed by a wide range of users.

Over time, the standard has been updated to accommodate changes in technology and the way people use the web. Today, URLs are an integral part of the web, allowing users to access a wealth of information quickly and easily.

Modern URL Usage and Changes

Over the years, the way people use the web has changed, with more and more people accessing online content through mobile devices. This has led to changes in the way URLs are used, with many websites developing mobile-specific URLs to improve the user experience on mobile devices.

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Mobile-specific URLs are designed to provide a better user experience on smaller screens, by optimizing the layout and content of the website for mobile devices. This can include features such as larger buttons and text, simplified navigation, and faster loading times.

The emergence of social media has also had an impact on URL usage, with many social media platforms using shortened URLs to make sharing links easier. Shortened URLs are created by taking a long URL and replacing it with a shorter one, usually using a service such as bit.ly or TinyURL.

Shortened URLs can be useful for sharing links on social media, where space is limited and long URLs can be difficult to read. However, they can also be used to hide the true destination of a link, which can be a security risk.

Despite these changes, URLs remain a fundamental part of the web, providing a way for users to access and share online resources. As the internet continues to evolve, it is likely that URLs will continue to play an important role in how we access and share information online.

Different Types of URLs

URLs, or Uniform Resource Locators, are the addresses used to identify resources on the internet. There are several types of URLs, each with its own unique characteristics and uses.

Absolute URLs

An absolute URL is a complete web address that includes all of the components required to access the resource. It begins with a protocol identifier, such as http or https, followed by the domain name, path, and any parameters that are required to access the resource.

For example, an absolute URL for the homepage of Google would be: https://www.google.com/. This URL includes the protocol identifier (https), the domain name (www.google.com), and the path (/) that leads to the homepage.

Absolute URLs are useful for linking to resources that are located on a different domain or server than the current page.

Relative URLs

Relative URLs are used to identify a resource relative to the location of the current page or file. Rather than providing the full web address, relative URLs only contain the information needed to access the resource relative to the current location.

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For example, if a webpage contains a link to an image located in the same directory, the relative URL would only need to include the filename and extension of the image, such as image.jpg.

Relative URLs are useful for linking to resources that are located within the same domain or server as the current page.

Protocol-relative URLs

Protocol-relative URLs (also known as protocol-relative links) are used in situations where the protocol used to access the resource may vary. These URLs specify the domain name and path but do not include the protocol identifier, allowing the protocol to be determined based on the context in which the resource is being accessed.

For example, a protocol-relative URL for the homepage of Google would be: //www.google.com/. This URL does not include the protocol identifier, allowing the protocol to be determined based on the context in which the URL is used.

Protocol-relative URLs are useful for linking to resources that may be accessed over both HTTP and HTTPS protocols, or for situations where the protocol used to access the resource may change based on the user’s browsing habits or network configuration.

URL Encoding and Decoding

Why URL Encoding is Necessary

URLs can only contain certain characters, with others requiring encoding to ensure they can be appropriately interpreted. URL encoding is a process that replaces characters that cannot be used in URLs with a sequence of characters that can be used.

Common URL Encoding Characters

Some of the most common characters that require encoding in a URL include spaces, quotation marks, and special characters such as ampersands and question marks.

Decoding URLs

URL decoding is the process of converting an encoded URL back to its original form, allowing it to be properly interpreted and accessed. This is typically done automatically by the browser or other software that is used to access the resource.


URLs are an essential part of the web, providing a unique address for every resource available online. Understanding how URLs work can help users navigate the web more efficiently, while developers can use this knowledge to create more user-friendly websites and applications. Whether you are accessing online content on a desktop computer or a mobile device, URLs provide a simple and effective means of accessing the vast array of resources available online.