Litmaps

Litmaps is a literature mapping tool from Wellington, New Zealand that turns a set of seed papers into an interactive citation map. Rather than returning a ranked list, it plots papers as nodes against time and citation relationships, then suggests the work that sits closest to what you have already collected. The map is the interface: what is dense, what is sparse and what is disconnected are all readable at a glance.
Why it matters
Ranked search results hide structure. A citation map shows which papers a field actually builds on, and which corners of it nobody has connected.
Sparse regions on a map are candidate research gaps, which makes the tool useful at the stage where a project is still being scoped.
Seeding from papers you already trust sidesteps the keyword problem, related work using different terminology still shows up through the citation graph.
Monitoring turns a one-off search into a standing alert as new papers attach themselves to an existing map.
Key features & advantages
Seed-and-expand discovery: start from one or more known papers and grow the map outward through citations and references.
Visual citation maps: papers plotted by date and connection, with the option to filter, cluster and re-centre as the question narrows.
Shared maps and collaboration on the Pro and Team plans, so a reading list can be handed to a group rather than exported as a bibliography.
Monitors: saved maps that alert on new matching literature.
Limitations & things to watch
Citation graphs reward age. Recent and preprint work is under-connected and can look peripheral on a map when it is not.
Coverage depends on the underlying bibliographic sources, non-indexed, paywalled and non-English work is invisible rather than flagged as missing.
A gap on the map may be a gap in the index, not a gap in the field.
The free tier caps map size tightly enough that serious use effectively requires the paid plan.