What a wikilink is

The syntax, in one line

You type [[Legibility]] in the middle of a sentence. That is a link to the note called Legibility. If the note does not exist yet, the link sits there unresolved until you write it — which is a feature: you can reference an idea before you have thought it through.

What it replaces

A folder makes you answer one question before you can save anything: where does this belong? That question has no good answer for most notes. A meeting about hiring that turned into an argument about metrics belongs in "hiring" and in "metrics" and in "that Tuesday", and a folder tree will let you pick one.

A wikilink sidesteps it. The note lives in one place and is reachable from every context that mentions it. You stop deciding where things go and start noticing what things touch.

Backlinks: the half people miss

A wikilink is bidirectional in effect, though you only write one end. When your note links to Legibility, that note now lists yours under "linked from". You did not edit it. You did not tag anything. The reference you made while writing about something else became structure.

This is why the graph on the homepage is not a visualisation feature bolted on top. It is a rendering of the link data that already had to exist for backlinks to work.

Unlinked mentions

A note that says the word "legibility" without brackets is not a link. Tools that support wikilinks usually surface these separately as unlinked mentions: places you talked about a thing without connecting to it. It is a useful list and a slightly uncomfortable one.

Where the idea breaks down

Three honest limits, because a technique described only by its advantages is being sold rather than explained:

• It needs titles you can remember. Wikilinks resolve by name. If your notes are called "Untitled 47", autocomplete cannot help you and neither can the graph.
• Renaming is a real operation. Every link pointing at the old title has to be rewritten. A tool that does not propagate a rename leaves you with silently broken links, which is worse than no links.
• It is not free structure. The links have to be written by you, while thinking. Nothing infers them. That cost is small and constant rather than large and deferred, which is the actual argument — but it is not zero.

Next: when a graph of these links starts being useful — with an honest answer about how many notes that takes.