Cartogenesis

Open source, free to use

Give it a seed. It builds the plates, the weather and the peoples.

Plates collide and erode, winds and currents decide where the rain falls, rivers find the sea, and realms take the ground between them — then it draws the map.

Open in the browser Download for Windows (recommended)

Free · Open source · Runs locally

A generated world map: a northern continent with a mountain range along its spine, a river system draining to a ragged southern coast, lakes, offshore islands, and the coast of a second continent at the right.
Seed 718106 · 62% ocean · 14 plates · 2048 cells · Atlas style
Rendered from the engine when this page was built, not drawn by hand.

One world, four readings

The same crop of the same world, drawn four ways. A map view chooses what is being shown; a map style chooses how it is drawn. Both are exported.

The Atlas style: land coloured by height from green lowlands to pale summits, relief shading, blue rivers and lakes, and bathymetric shading in the sea.
Atlas — height in colour, relief raked by a low sun, rivers drawn with a pen sized by their discharge.
The biomes view of the same crop: white sea ice along the top, grey-green tundra across the northern half of the continent, olive steppe and tan desert in the south, and dark green forest on the southern coasts.
Biomes — Köppen classes from the season's temperature and rainfall: sea ice, tundra, steppe, desert, forest.
The political view of the same crop: the continent in one teal realm with two smaller ones on its west coast, an offshore island in lavender, and several more realms along the right-hand edge.
Political — realms grown from their capitals along watersheds, rivers and coasts, so borders sit where the ground divides.
The Pen and ink style of the same crop: black hachures on cream paper for the relief, contour rings offshore, a stippled band of sea ice, and hairline borders.
Pen and ink — the same terrain as hachures, coastal contour rings and stipple, drawn rather than tinted.

Three things it works out

Crops from the same world, cut out of the 2048 render at its own pixels rather than scaled down to fit, so the pen is the one the renderer draws with.

The rainfall view across a mountain range running from the lower left to the upper right. A narrow green strip marks the wet seaward coast, and the ground immediately behind the crest is the palest in the frame.
  1. Windward coast, the wettest ground here
  2. The crest, running south-west to north-east
  3. Its lee, the driest ground in the frame
A rain shadow. Moist air carried onto the coast rises over the range, rains out on the windward flank and comes down the far side dry. Rainfall view.
A dense river network draining to a large lake. The headwaters are hair-thin threads; the channel thickens at each junction, and the reach entering the lake is several times the width of a thread.
  1. Headwaters, a hairline wide
  2. Each tributary widens the trunk below the junction
  3. The mouth: the widest channel on this world
A river widening with its discharge. Width follows the square root of the flow it carries, which is what Leopold and Maddock measured on hundreds of gauged rivers, so a trunk is about five times a headwater and every junction shows.
A continental rift flooded by the sea: a long narrow ridge standing above a drowned trough, a nearly enclosed round gulf beside it, and further east a long inlet pinched in the middle by a low neck of land.
  1. A shoulder, standing above the trough it flanks
  2. A deep segment, flooded to a gulf
  3. A sill between two segments
A rift breaking into gulfs. A continental rift is cut along its length into segments, each with its own depth and its own raised flank, and the joins between them stand as low sills. The sea floods the deep segments and stops at the sills, so the rift reads as a chain of gulfs rather than one straight trench.

What you get

Views
Fifteen: the fantasy map, political and peoples, elevation, biomes, temperature and rainfall by season, plates, currents, winds.
Styles
Eleven for the map: atlas, vellum, ink wash, nautical chart, pen and ink, Mars, and a colour-blind-safe palette.
Themes
Fifteen for the window: light, dark, high contrast, colour-blind, and styled sets from Nautical to Hitchcock.
Editing
Every generated name and border can be overridden, and the overrides are kept with the world.
Saves
A save holds the finished world, and the same file opens in the browser and on the desktop.
Export
PNG or WebP, up to 4096 × 4096.
Resolution
512 to 4096 cells across; the browser starts at 512, the desktop app at 1024.
Acceleration
Optional, for erosion and export rendering: WebGPU in the browser, OpenGL on the desktop.

Practical details

Running it in a browser

Recent Chrome, Edge, Firefox or Safari. The first visit downloads about 4.5 MB and is cached after that; nothing you make is uploaded anywhere.

The optional graphics-card acceleration uses WebGPU where the browser offers it.

Sizes, formats and speed

An export re-runs the whole pipeline at the size you ask for rather than enlarging what is on screen, so the detail is real; 4096 wants a few gigabytes, which is why the browser stops at 2048 on a phone.

WebP is about a quarter of PNG's size and softens thin rivers and borders very slightly. With a graphics card, a 1024 world takes about twenty seconds on a 2026 phone and 2048 about a minute and a half.

The Atlas is a work in progress

Today it lists a world's realms and landmarks, lets you rename them and place labels, and stops there. A full atlas is planned for a later release, targeting 4.0: named continents, seas, bays, straits and ranges, with labels set out the way a printed map sets them. Names you give now are kept with the world.

Desktop versionWindows

Bigger worlds, more threads and no download before you start. Portable zip or installer. The installer is unsigned, so Windows shows a SmartScreen warning the first time; choose “More info”, then “Run anyway”.

Get the latest release ↗