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We’ve lived with the web for almost three decades. As a result, most of us are familiar with links: elements in one document that point to other documents. But there’s more to links than what we see on the web. As hypertext note-taking systems become more popular, we must expand our understanding of links.

Let’s recap how web links work. Links in a web page are explicitly defined by its author. Elements that serve as link origins can be words or images. Destinations can be anything a web browser can display and can be located with a Uniform Resource Identifier (URI). It’s a simple yet powerful scheme.

But by default, web links are very basic. Clicking on a link will load the destination document in your browser, replacing the origin document. The relationship is one-way: you can go back using your browser’s back button, but in most cases, there won’t be an explicit link at the destination pointing back to the originating document.

This simplicity contributed to the web’s popularity: the system is easy to learn for both authors and readers. However, there’s more to links than this. Hypertext researchers have explored several other types of links since the late 1960s, and some are now available in hypertext note-taking apps like Roam Research, Obsidian, and Logseq.

Here are five different types you should know about:

  • Wiki-style links are like web links: you select a word or phrase and point it to another note (or any asset you can access through a URI.) While both web links and wiki-style links are explicitly defined, the latter are much easier and faster to use, resulting in a more fluid linking process.

  • Conversely, implicit links aren’t intentionally defined. Instead, the system creates them for you based on metadata such as a note’s title or creation date. For example, Obsidian lets you see all notes in your system that include a phrase that matches your current note’s title.

  • Backlinks are another way to see which notes connect to your selected note, but in this case, you see a list of all the notes that explicitly link to the current note. Notes in Roam Research include a list of backlinks at the bottom of each note.

  • Block-level references are explicit links, but instead of pointing to a whole document or note, they point to blocks (e.g., individual paragraphs) within that destination. (It’s worth noting that the web supports block-level references.)

  • Transclusions are something else entirely. Rather than “taking you” to the destination document, transclusion inserts the destination’s content (be it a whole note or a block) into the body of the origin note. Changes to the destination are reflected in the transcluded version. (I realize this sounds a bit mind-bendy, so I’ve made a YouTube video that explains how it works in Obsidian.)

Hypertexts have great potential to improve your cognitive abilities. However, most research has focused on how people read hypertexts, not how they create them. It’s understandable, given that hypertext authoring has been a specialized activity.

So, it’s exciting to see how hypertext note-taking apps bring these esoteric ideas to the mainstream. Primed by the web, we’re now better positioned to exploit these technologies’ potential — and it starts with understanding different types of links.