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Getting Started

What Is New Horizons?

New Horizons is a mod creation framework for creating custom planets in the game Outer Wilds by Mobius Digital. It primarily uses JSON files, along with a few XML files to define content.

It’s strongly recommended you get VSCode to edit your files, as it can provide syntax and error highlighting.

Try Out New Horizons

Making an entirely separate addon can get a little complicated, so New Horizons provides a way to play around without the need to set up a full addon. If you want to make a full project, see Creating An Addon.

To get started, navigate to your mod manager and click the ⋮ symbol, then select “Show In Explorer”.

Select "Show in explorer"

Now, create a new folder named “planets”. As the name suggests, New Horizons will search the files in this folder for planets to generate.

Making Your First Planet

To get started, create a new file in this folder called wetrock.json, we’ll explain what that .json at the end means soon. Open this file in VSCode (you can do so by right-clicking the file and clicking “Open with Code”) Once in VSCode, paste this code into the file:

"name": "Wetrock",
"$schema": "",
"starSystem": "SolarSystem",
"Base": {
"groundSize": 100,
"surfaceSize": 101,
"surfaceGravity": 12,
"hasMapMarker": true
"Orbit": {
"semiMajorAxis": 1300,
"primaryBody": "TIMBER_HEARTH",
"isMoon": true,
"isTidallyLocked": true
"Atmosphere": {
"size": 150,
"fogTint": {
"r": 200,
"g": 255,
"b": 255,
"a": 255
"fogSize": 150,
"fogDensity": 0.2,
"hasRain": true

Here we can see we have a planet object, which name is “Wetrock”, and is in the “SolarSystem” (Base-game) star system.
It has an object called Base, which has a groundSize of 100, and a surfaceSize of 101, and the list continues on.

Alright so now that we understand how the file is structures, let’s look into what each value actually does:

  • name simply sets the name of the planet
  • $schema we’ll get to in a second
  • starSystem specifies what star system this planet is located in, in this case we’re using the base game star system, so we put “SolarSystem”
  • Then it has an object called Base
    • Base has a groundSize of 100, this generates a perfect sphere that is 100 units in radius as the ground of our planet
    • It also has a surfaceSize of 101, surface size is used in many calculations, it’s generally good to set it to a bit bigger than ground size.
    • surfaceGravity describes the strength of gravity on this planet, in this case it’s 12 which is the same as Timber Hearth
    • hasMapMarker tells new horizons that we want this planet to have a marker on the map screen
  • Next it has another object called Orbit
    • semiMajorAxis specifies the radius of the orbit (how far away the body is from its parent)
    • primaryBody is set to `TIMBER_HEARTH“, this makes our planet orbit timber hearth
    • isMoon simply tells the game how close you have to be to the planet in map mode before its name appears
    • isTidallyLocked makes sure that one side of our planet is always facing timber hearth (the primary body)
  • Finally, we have Atmosphere
    • Its size is 150, this simply sets how far away from the planet our atmosphere stretches
    • Its fogTint is set to a color which is an object with r, g, b, and a properties (properties is another word for keys)
    • fogSize determines how far away the fog stretches from the planet
    • fogDensity is simply how dense the fog is
    • hasRain makes rainfall on the planet

What’s a Schema?

That $schema property is a bit special, it instructs VSCode to use a pre-made schema to provide a better editing experience. With the schema you get:

  • Automatic descriptions for properties when hovering over keys
  • Automatic error detection for incorrect data types or values
  • Autocomplete, also called IntelliSense

The schema we’re using here is the Celestial Body Schema, but there are many others available in the Schemas section of the left sidebar.

Testing The Planet

With the new planet created (and saved!), launch the game through the mod manager and click resume expedition. If all went well you should be able to open your map and see wetrock orbiting Timber Hearth.

If you run into issues please make sure:

  • You placed the JSON file in a folder called planets in the New Horizons mod folder
  • There are no red or yellow squiggly lines in your file

Creating An Addon

Making a GitHub Repository

To get started, you’ll need to fork the the New Horizons addon template

  • Set the Name to your username followed by a dot (.), followed by your mod’s name in PascalCase (no spaces, new words have capital letters). So for example if my username was “Test” and my mod’s name was “Really Cool Addon”, I would name the repo Test.ReallyCoolAddon.
  • The description is what will appear in the mod manager under the mod’s name, you can always edit this later
  • You can set the visibility to what you want; But when you go to publish your mod, it will need to be public

Open The Project

Now clone the repository to your local computer and open it in your favorite editor (we recommend VSCode).

Project Layout

  • .github: This folder contains special files for use on GitHub, they aren’t useful right now but will be when we go to publish the mod
  • planets: This folder contains a single example config file that destroys the Quantum Moon, we’ll keep it for now so we can test our addon later.
  • .gitattributes: This is another file that will be useful when publishing
  • default-config.json: This file is used in C#-based mods to allow a custom options menu, New Horizons doesn’t support a custom options menu, but we still need the file here in order for the addon to work.
  • manifest.json: This is the first file we’re going to edit, we need to fill it out with information about our mod
    • First you’re going to set author to your author name, this should be the same name that you used when creating the GitHub repo.
    • Next, set name to the name you want to appear in the mod manager and website.
    • Now set uniqueName to the name of your GitHub Repo.
    • You can leave version, owmlVersion, and dependencies alone
  • NewHorizonsConfig.dll: This is the heart of your addon, make sure to never move or rename it.

Testing The Addon

In order for the addon to show up in the manager and subsequently be loaded into the game, you’ll need to ensure that it’s located in %APPDATA%\OuterWildsModManager\OWML\Mods (or ~/.local/share/OuterWildsModManager on Linux). How you choose to do this is up to you, you could manually copy the mod folder over every time, you could setup an automated VSCode Launch Configuration to do it every time you press F5, or you could simply keep your mod in that folder. The last option while although the easiest is not recommended as downloading another version of your mod can overwrite your current working copy.

Once put in the Mods folder, the manager will display your mod without a description or download count, you can then launch the game to see if your planets load in.

Checking In-Game

Now when you click “Start Game” and load into the solar system, you should be able to notice that the quantum moon is gone entirely, this means that your addon and its configs were successfully loaded.