You might not know "deep links" by name, but you've almost certainly used them before. This digital navigation tool can be used to make content more accessible or less accessible. It can be a boring click-farming gadget or used in some really creative ways.

So, what is a deep link?

Deep links are links from within one website or application to another website or application. For example, if you found this article from a link in a news email app or a link on another website, that's deep linking. This article contains links to within other websites. That's deep linking too.

As someone navigating the web, deep links are ubiquitous and taken for granted. But, if you contribute to the web ecosystem through site-building and app development, deep linking is a little more complicated and a lot more interesting.

The basic kinds of deep linking are linking between websites, web-to-app linking, app-to-web linking, and app-to-app linking. All of these increasingly complex solutions solve increasingly complex problems.

Linking Between Websites

Linking from one website to within another website is probably the most familiar kind of deep linking. It's also the easiest and often comes up in content creation.

Sites that link to each other are like the scene in "Miracle on 34th Street" when the Kohl's Santa suggests that holiday shoppers get some items from other stores. This is helpful for the shoppers because they get what they want, but it ends up helping the Kohl's by building trust.

Websites like to keep readers on the page, but they also like to provide the best possible information to readers. Sometimes, that means linking to another website. So, deep linking helps readers get the information they want, helping websites rank better on search engines for delivering useful information.

exampe of linking tool in CMS

Because deep linking is such a common practice on websites, there's an easy-to-use tool for it in most content management platforms and word processors. But that's not the only use.

Deep linking is increasingly used to connect spatial websites. In this case, clicking on items in the world transports users to other virtual spaces, like touching a portkey in the Harry Potter Universe.

A deep link from a virtual world in the Spatial platform to a virtual world in the Frame platform.

Web-to-App Linking

Web-to-App linking is usually done when content is more discoverable on the web but can only be done (or can best be done) within an app. An immediate example is discovering and downloading apps themselves.

Suppose you're browsing the web and discover an app that seems interesting. You tap the link, but your web browser doesn't take you to information about the app. In fact, your browser closes, and your smart device's app store opens, taking you directly to the page for the app that you discovered on the web page. That's the result of deep linking.

This kind of deep linking is a little more complicated. It actually requires creating a web address to a location within an app, which means a little specialist coding. What this will look like is different based on the operating systems that the app is optimized for. The example below is for deep linking a Microsoft Windows app.

Code provided by Microsoft for deep linking from a website to within an app.

Web-to-app linking is also used to share exclusive content. An email containing a deep link can be sent to select app holders. When they click on the deep link, it can take them to parts of the app that not everyone can access.

App-to-App Linking

As we live our lives within apps, it makes sense that the content we consume passes from one app to the next. App-to-App linking allows this. One common example might be getting a link to a YouTube video sent to you within a text message. You click on the link, and it opens in the YouTube app on your smart device.

Building a link like this on your own can be complicated, but commonly used apps have pre-made App Programming Interfaces (APIs) that let them work together. App-to-App linking isn't just for sending content to one another. A good API can also increase security for apps that hold sensitive content.

Security APIs require one person to sign in to one app using another app for double security. For example, if you use the PayPal prepaid app, you know that that app often requires you to sign in using the standard PayPal app. This is an example of double-authentication security through app-to-app deep links.

App-to-App linking also has a place in the Internet of Things. It's how smart assistants like Amazon's Alexa can send content to your mobile device or run tasks in apps while you're otherwise occupied.

App-to-Web Linking

There's not a whole lot to say about this one. It works a lot like linking between web pages because most apps are already connected to the internet anyway. Common examples might include clicking a link in your calendar app to open a Zoom call in your browser. Or using a button in the Duolingo app to share an achievement on Twitter.

In the second case, there's a little more back-end work from Duolingo. After all, they needed to create the artwork and text that makes up the default post. Research for this article didn't include tearing apart Duo's deep link coding, but there was probably an automated movement of this art and text through your device's clipboard. Still, not too messy.

You just tap the blue text, right? It's easy to take deep linking for granted, but think about where we were without it. Manually opening apps because we saw something cool online? Or finding something cool online and not knowing how to share it? The dark ages.