Overland Map Generator
The thing that gives a made-up map away is the water. A river that climbs a hill, forks the wrong way or joins its own tail looks wrong to anybody who has read a real map, and it is one of the few things about an invented landscape that can actually be checked. Here every river leaves each cell for the lowest of its neighbours and only if that neighbour is lower, so a course cannot climb and cannot loop — and the finished map is walked again afterwards to confirm it. Regions are grown outwards from their seats until they meet, so between them they cover the mainland and none of them is stranded on an island.
What this generator does
Builds a height field, floods it to the water line you asked for, and then works out where the water on every land cell goes. Anything carrying enough water is drawn as a river and traced from its head to the sea or to a lake. Land is divided by growing each region outwards from its seat at the same rate until the regions meet.
How to use this tool
- Choose how big the map is and how much of it should be sea.
- Choose how many named regions to divide the land into.
- Draw the map, and read the rivers and regions listed underneath it.
- Copy the link if you want somebody else to see this exact map, or the text version for your notes.
Understanding the controls
- Map size
- Between 16 and 40 cells across. Larger maps have room for longer rivers and more separate landmasses.
- Sea
- The share of the map below the water line. The line is placed by ranking every cell by height, so asking for 40% sea gives 40% sea rather than something near it.
- Regions
- How many named territories to divide the mainland into. Asking for more than the land can hold gives as many as fit.
- Repeat word
- The word this map was built from. Anyone opening the same link gets the same map, on any device.
Common use cases
- A country for a tabletop campaign that holds together when players ask where the river goes
- A hex-crawl or overland-travel map with regions to move between
- A setting sketch for a novel, with somewhere for the borders to be argued over
- Handing the same map to everybody at the table from one link
- Teaching how water finds its way downhill, on a landscape nobody has seen before
How this generator works
Water leaves a cell for the lowest of its eight neighbours, and only when that neighbour is strictly lower. That single rule is what makes the promise checkable: a course that drops at every step can never return to a place it has already been, because it would have to climb back up to it. A cell with no lower neighbour keeps its water and is drawn as a tarn. Afterwards every course is walked again from the finished map and each step compared with the one before, and each region seat is confirmed to lie on the largest connected run of land.
Randomness and fairness
The map is built from a repeat word, and the word is drawn from your browser's secure generator unless you type one of your own. That makes a map reproducible, which is the point of it, and it means the sequence behind it is deterministic and not cryptographic — it is for maps, not for anything that needs to be unguessable.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Rivers do not braid, meander or flood — each cell sends its water one way, which is a simplification of a real catchment.
- Rainfall is not modelled, so a river's size follows how much land drains through it rather than the weather over it.
- Regions are grown by distance from their seats, so their borders follow the land rather than any history of who fought whom.
- Islands off the mainland are drawn but never given a region, because the promise is that a region can be walked to.
Privacy and your data
The map is built on your device and nothing about it is transmitted or stored. The repeat word is a short label this page made or you typed, and it is the only thing that ever appears in the address; it is never measured.
Related generators
- Terrain Heightmap GeneratorSmoothly interpolated value-noise height fields with a movable water line, and continuity checked rather than assumed.
- Cave Map GeneratorOrganic cave layouts from cellular-automata smoothing, with every pocket joined so the whole map is walkable.
- Fantasy Calendar System GeneratorA whole invented calendar — months that add up to the year, a leap rule that holds it still for a thousand years, and moons that come back round.
- Dungeon Layout GeneratorRoom-and-corridor dungeons built by binary space partitioning, where connectivity is structural rather than checked afterwards.
- Star System GeneratorAn invented planetary system whose numbers agree with each other: every year follows from the planet’s distance and its star’s mass, and the habitable zone follows from the star’s brightness.