Links
Backlinks and wikilinks: the mechanic that turns notes into a system
A wikilink is a link you write as [[Note title]]. A backlink is the automatic reverse: when note A links to note B, note B shows that A references it, with the surrounding sentence for context. You write links in one direction and the system maintains both, which is what makes linking cheap enough to actually do.
The syntax
Wikilink syntax came from wikis and was popularised for personal notes by Roam and Obsidian. It is deliberately tiny, because a link you have to think about is a link you will not make.
[[Note title]]— link by title. Autocomplete usually fires on the second bracket.[[folder/Note title]]— link by path when two notes share a title.[[Note title|what to call it here]]— an alias, so the sentence still reads properly.[[Note title#Heading]]— jump to a specific heading in the target note.![[Note title]]— embed the note's content inline rather than linking to it.![[image.png]]— embed an attachment.
Why the reverse direction is the point
Writing a link is a decision you make once, in one place, while writing. Maintaining the reverse by hand is work you would never keep up, which is why manually cross-referenced note systems collapse: the index goes stale and stops being trustworthy.
Automatic backlinks remove that cost entirely. The consequence is behavioural rather than technical — because linking is free, you link far more, and the network gets dense enough to be genuinely useful. A note-taking system's value is roughly the square of how connected it is, and connection is bounded by how much effort each link costs.
Unlinked mentions, and links to notes that don't exist
Two related features do most of the remaining work. Unlinked mentions find places where a note's title appears as plain text without being a link — usually things you wrote before that note existed. Turning them into links is often the fastest way to densify an old vault.
Unresolved links are the other direction: [[A note I have not written]] is valid, and it appears in the graph as a ghost node. This turns out to be a good way to work — write the link while the thought is live, create the note later. In Nodum, clicking the ghost node creates the note and the backlink resolves on the spot.
How Nodum implements it
Link extraction happens server-side on every save, writing into a links table with source, target and an unresolved flag. That is what makes backlinks, unlinked mentions, the graph and the orphan filter all query-cheap rather than something recomputed by scanning files.
The backlinks pane shows linked mentions with a context snippet, unlinked mentions, and outgoing links, on every note. Because links live in a table rather than being parsed on demand, renaming a note or importing a vault of two hundred notes resolves links across the whole batch rather than file by file.
Questions people ask
What is a backlink in a note-taking app?
A backlink is the automatic reverse of a link you wrote. If note A contains [[Note B]], then note B displays that A references it — usually with the sentence around the link for context. You maintain one direction; the app maintains the other.
What is the difference between a wikilink and a markdown link?
A markdown link, [text](path/to/file.md), points at a file path and breaks when the file moves. A wikilink, [[Note title]], points at a note by title and is resolved by the app, so it survives moves and renames and can be created before the target note exists.
What are unlinked mentions?
Places where a note's title appears as plain text somewhere else in the vault without being a link. They are usually text written before the note existed. Reviewing them and converting the relevant ones into real links is the quickest way to connect an existing collection of notes.
Related reading
Comparing specific tools
- Nodum vs ObsidianNodum is a free, MIT-licensed Obsidian alternative for the web: same [[wikilinks]], same backlinks, same graph — no install, and you can read the source.
- Nodum vs NotionNodum is a free, open-source Notion alternative built on plain markdown, [[wikilinks]] and a knowledge graph — self-hostable, exportable, no per-seat pricing.
- Nodum vs LogseqNodum and Logseq are both open source and both link notes. Nodum is a document editor in the browser; Logseq is a local-first outliner. Here is the honest split.
All 18 are on the alternatives index. Terms used on this page are defined in the glossary.
Start tying things together.
A vault takes about ten seconds to make. Bring notes with you, or start with one.