What is a URL

Uniform Resource Locator

"URL" is a way of identifying the location of a file on the Internet. This is what is used to open websites, download images, videos, software programs, and other types of files

Opening a file on your own computer is as simple as double-clicking it, but to open files on remote computers, like on the Internet or a Web Servers, we must use URLs so that our web browser knows where to look

Uniform Resource Locator's are most commonly abbreviated as URLs but they're also called website addresses when they refer to URLs that use the HTTP or HTTPS protocol

URL is usually pronounced with each letter spoken individually (i.e. U -R - L, not earl). It used to be an abbreviation for Universal Resource Locator

Examples of a URL

You're probably used to entering in a URL, like this one for accessing Google's website:
Or other examples:

The entire address is called the URL. You can even get super specific and open the direct URL to an image, like this one that points to RSH's image

If you open that link you can see that it starts with https://
And has a regular looking URL like the examples above, but also has other text and slashes in order to point to the exact folder and file where the image resides on the web-site's server

The same concept applies when you're accessing a router's login page; the router's IP address is used as the URL in order to open the configuration page

Most of us are familiar with these types of URLs that we use in a web browser like Firefox or Chrome, but those are not the only instances where you might need a URL

In all of these examples, you're using the HTTP protocol to open the website, which is the most popular that most people encounter, but there are other protocols you could use too, like FTP, TELNET, MAILTO, and RDP A URL can even point to local files you have on a hard drive
Each protocol may have a unique set of syntax rules in order to reach the destination

Structure of a URL

A URL can be broken down into different sections, each section serving a specific purpose when accessing a remote file

HTTP and FTP URLs are structured the same, as protocol://hostname/fileinfo

For example, accessing an FTP file with its URL might look something like this:
Which, aside from having FTP instead of HTTP, looks like any other URL you might encounter on the Web

Let's use the following URL, which is Google's announcement of a CPU flaw, as an example of an HTTP address and identify each part:

https is the protocol (like FTP is a protocol) that defines the type of server that you're communicating with
security is the hostname used to access this specific website
googleblog is the domain name
com is what's referred to as the top-level domain (TLD), some others of which include .net, .org, .co.uk, etc
/2018/01/ represents the directories used to organize the webpage or file. On the web server that's holding the website files, these would be the actual folders that you'd click through to find the file that this URL is specifying
todays-cpu-vulnerability-what-you-need.html is the actual file that the URL is pointing to. If you were trying to load an image, audio file, or another file type instead of an HTML file, then the URL would end in that file extension (like a PNG or MP3)
security.googleblog.com as a group is called the Fully Qualified Domain Name (FQDN)

To learn more see Why URL Structure is Important for SEO?

URL Syntax Rules

Only numbers, letters, and the following characters are allowed in a URL: ()!$-'_*+
Other characters must be encoded (translated to programming code) in order to be accepted in a URL
Some URLs have parameters that split the URL away from additional variables. For example, when you do a Bing search for rshweb:

The question mark you see is telling a certain script, hosted on Bing's server, that you want to send a specific command to it in order to get custom results. The specific script that Bing uses to execute searches knows that whatever follows the ?q= part of the URL should be identified as the search term, so whatever is typed at that point in the URL is used to search on Bing's search engine

You Will now start to see the similar behavior in URL's Like in this YouTube search for best cat videos:
Although spaces are not allowed in a URL, some websites use a + sign, which you can see in both the Google and YouTube examples. Others use the encoded equivalent of a space, which is %20

URLs that use multiple variables use one or more ampersands after the question mark. You can see the example here for an Amazon.com search for Windows 10:

Parts of a URL are case sensitive — specifically, everything after the domain name (the directories and file name). You can see this for yourself if you capitalize the word "tools" in the example URL from my site that we deconstructed above, making the end of the URL read /free-driver-updater-Tools.htm. Try to open that page here and you can see that it doesn't load because that specific file doesn't exist on the server

More Information on URLs

If a URL points you to a file that your web browser can display, like a JPG image, then you don't have to actually download the file to your computer in order to see it. However, for files that aren't normally displayed in the browser, like PDF and DOCX files, and especially EXE files (and many other file types), you'll be prompted to download the file to your computer in order to use it

URLs provide an easy way for us to access a server's IP address without needing to know what the actual address is. They're like easy-to-remember names for our favorite websites. This translation from a URL to an IP address is what DNS servers are used for

Some URLs are really long and complex and are best used if you click it as a link or copy/paste it into the browser's address bar. A mistake in a URL could generate a 400-series HTTP status code error, the most common type being a 404 error Page

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