Ostranauts How to Mod: Step-by-Step Modding Tutorial

Why Learning Ostranauts How to Mod Changes Everything

Ostranauts is built around an unusual promise: every piece of game data is exposed as plain text, which means Ostranauts how to mod is something any player can pick up without compiling a single script. The game shipped to Steam with a public 1.0 release on August 3, 2026, and developer Blue Bottle Games documented the underlying .json and .txt structure so the community can rebalance prices, redesign interiors, and add entirely new ship parts without ever touching the engine.

Modding in Ostranauts matters because the base game ships in a deliberately austere neon-noir universe where every trader, every hull plate, and every coffee cup is data-driven. When you learn the workflow you can tweak crew needs, raise salaries for unpopular jobs, or rebalance the K-Leg loan so a new run no longer feels like indentured servitude. According to community data on the official wiki, the same approach scales from a five-minute balance patch all the way to total conversion overhauls that swap out the entire economy.

One thing veterans point out is that Ostranauts how to mod matters more than any in-game toggle UI would suggest, because there is no built-in browser, no Steam Workshop, and no mod menu inside the pause screen. Everything you do lives in the file system, which sounds intimidating but actually makes the workflow easier to debug once you understand it. A loose .json patch can be edited in any plain text tool, dropped into the Steam folder, and tested on the next reload without ever rebooting the game client.

That accessibility is why the Ostranauts how to mod ecosystem grew steadily throughout Early Access, with community patches ranging from a simple coffee price tweak to full crew-AI overhauls that change how NPCs argue, sleep, and request salary bumps. Because the developer has stated publicly that mod support will remain a post-1.0 priority, the workflow covered here is unlikely to shift drastically after launch — a stable foundation that makes the time you invest learning it pay off across future patches.

Preparing Your Game Files for Modding

Before you touch any folder, you need a clean baseline. A fresh game install lives inside Steam's common directory, and your save files live in a separate UserData path — conflate the two and you risk wiping a 200-hour career after a single misclick.

Backing Up Saves and Files

Copy the entire Ostranauts save folder to a date-stamped backup drive before adding any mod. Community testing shows a corrupted save often surfaces only after the next autosave, by which point your last clean version is the one you made manually. A second copy of the entire common\Ostranauts install is good insurance if you plan to edit base data files in place.

Verifying Game Integrity

After a backup, right-click the game in Steam, choose Properties → Installed Files → Verify integrity of game files. This replaces any base file Steam thinks is broken and gives you a known-good comparison point. Skipping this step is the single most common reason players blame a mod for crashes actually caused by a partial download or an interrupted update.

Installing the Mod Loader and Folder Framework

Ostranauts does not ship with a third-party mod loader the way Bethesda or Paradox titles do. The "loader" is just the Mods folder under StreamingAssets, and any compatible .json or .txt placed inside it is applied automatically on the next launch.

Step 1 — Locate the Game Folder

Open Steam, right-click Ostranauts, click Manage → Browse local files. The window that opens is your root install folder; inside it you will see Ostranauts.exe, a _Data directory, and a UnityCrashHandler64.exe. The mod folder sits inside that structure and is created automatically the first time the game boots in version 1.0.0.7 or later, although several pre-1.0 builds already created the directory on first save.

Step 2 — Create or Confirm the Mods Directory

Navigate to Ostranauts_Data\StreamingAssets\Mods. If the folder is missing, create it manually with the exact capitalization shown — Windows allows lowercase variants but the game has been observed ignoring them on certain Linux/Proton installs. Inside this folder, every mod lives as its own subdirectory so load order and isolation can be controlled cleanly.

For a more advanced walkthrough of multi-file packs and merge-tags, the creating a custom mod guide explains how the parser reconciles overlapping entries, while our mod installation primer covers the same process from a Steam-library perspective for players who prefer keeping their game folder pristine.

Locating the Game Data Files You Will Edit

Every number you can tweak lives in a .json file under the base StreamingAssets directory. The trick is knowing which file owns which system so you can overwrite only the field you intend to change.

A useful workflow is to copy the file you want to edit into your mod folder, then delete every key except the ones you want to change. The game performs a full-file replace, so a stripped-down override with only two or three fields merged into base data is more stable than a copy with 5,000 untouched lines, where one stray comma can break the entire JSON parser and brick your game on launch. Players who are still getting comfortable with the base loop can revisit the vanilla economy in our beginner guide and compare it against their modded values once changes start landing.

Understanding Load Order and Conflict Resolution

Once a mod sits in the correct folder, loading is automatic — there is no in-game mod manager checkbox in version 1.0.0.7. The game reads the Mods directory alphabetically on startup, so a folder named zzzz_last always wins over a folder named aaa_first for any field they both define.

If you want a temporary disable without deleting the folder, prefix the directory name with a hyphen, for example -MyMod. The game skips any folder whose name starts with a hyphen because the prefix marks the entire tree as a disabled stub. This trick is the cleanest way to A/B test balance changes against the vanilla baseline during long careers, which is also why most veteran players rely on it instead of moving files in and out of the directory repeatedly.

Community testing suggests that the order of files inside a single mod folder does not matter — only the folder name determines its load position relative to other mods. This makes deep folder structures safe to use for organization, but bad for controlling which patch "wins" in a conflict.

Creating and Testing Your First .json Mod

Start small: pick one number that bothers you, copy the relevant entry into your mod folder, change the value, save, and relaunch. A working test mod takes less than five minutes and proves every link in the chain is functional before you invest in a larger project.

Editing a .json File

Open any .json in a code editor such as VS Code or Notepad++ — never use Word or rich-text editors, because they silently insert smart quotes that the JSON parser will reject. Modify only the fields you fully understand; an items.json line for Coffee contains price, mass, thirst restore, and a sprite reference, so changing just price leaves the rest intact. According to developer commentary on the official wiki, the same parser rules apply whether you are editing a single line or a 10,000-line pack.

Saving the Test Mod

Save the edited file as plain UTF-8 .json and place it in Mods\TestMod\data\items.json. Launch the game, load a save, and check whether the value you changed behaves as expected in the K-Leg market. If the game fails to start, the most likely culprit is a syntax error in your JSON; running the file through a free online validator catches 90% of typos in seconds.

Troubleshooting Common Mod Problems

Even with a clean install, mods can break the game in subtle ways that look like vanilla bugs. Before you blame any single mod, always reproduce the issue with the Mods folder temporarily renamed to -Mods.

If a single mod bricks your install, you can usually recover by deleting the offending folder, then renaming -Mods back to Mods. For deeper salvage strategies when a career save is already on the brink, the how to salvage ships guide covers the in-game recovery options that let you rebuild after a mod-induced economy crash.

If you are still learning what the base game should feel like, our Ostranauts how to play walkthrough gives a side-by-side view of vanilla behavior so you can spot regressions faster than trial-and-error would allow.

Frequently Asked Questions

Do I need a separate mod manager for Ostranauts how to mod?

No. As of the 1.0 release on August 3, 2026, the game reads a plain Mods folder inside the install directory. Any compatible .json or .txt placed there loads automatically on the next launch — no third-party launcher required.

Where is the Ostranauts mod folder located?

It lives at <install>\Ostranauts_Data\StreamingAssets\Mods\, where <install> is your Steam common\Ostranauts root. If the folder does not exist, create it with the exact spelling shown, because Proton and Linux installs have been reported ignoring lowercase variants.

Can mods corrupt my saves?

Yes, if you overwrite econ.json or crewData.json mid-career with values the save can no longer reconcile. Always back up the %USERPROFILE%\AppData\LocalLow\Blue Bottle Games\Ostranauts\ folder before applying changes that affect crew needs, salaries, or loan terms.

How do I disable a mod without deleting it?

Prefix its folder name with a hyphen, e.g. -MyMod. The game skips any folder starting with -, which makes A/B testing balance patches much faster than moving files in and out of the directory.

What is the safest first mod to try when learning Ostranauts how to mod?

A single-line price edit in items.json is the safest starting point because its effect shows up in the very next K-Leg market visit. Once your edit round-trips cleanly, you can graduate to multi-file packs and total conversion projects with confidence.