RimWorld vs Oxygen Not Included: Drama or Thermodynamics

Play RimWorld if you want stories about people. Play Oxygen Not Included if you want an engineering problem that fights back. Both are top-tier colony sims and the choice between them is not about quality, it is about whether you would rather manage a cast or manage a closed thermodynamic system.

They get shelved together and recommended interchangeably, which does a disservice to both. The overlap is the base building. Almost everything else diverges.

What is the core difference?

RimWorld simulates people. Oxygen Not Included simulates physics. In RimWorld, the thing that will kill your colony is usually a person: a mood break, a lost fight, a surgeon who was somewhere else. In Oxygen Not Included, the thing that will kill your colony is a temperature gradient you did not notice eight hours ago.

Klei describes ONI as a game where <cite index="111-1">scarcities of oxygen, warmth, and sustenance are constant threats to your colony's survival as you guide colonists through subterranean asteroid living.</cite> That is an accurate description of an engineering brief. RimWorld's own pitch calls it a story generator, which is an accurate description of something else entirely.

How do they compare feature by feature?

The DLC comparison flatters ONI. RimWorld's five expansions run $19.99 to $24.99 each. Klei's packs, including Spaced Out!, The Frosty Planet Pack, The Bionic Booster Pack, The Prehistoric Planet Pack, and The Aquatic Planet Pack, are generally smaller additions built around new starting worlds, and the base game discounts hard. PCGamesN noted ONI at <cite index="104-1">70% off during one sale, putting it at $7.49,</cite> which RimWorld has never approached.

Which one is harder?

Oxygen Not Included, for most people, and the difficulty is a different shape. RimWorld's challenge is reactive. A raid arrives, a plague hits, someone snaps, and you respond with the tools you have. You can usually see the problem when it starts.

ONI's challenge is anticipatory and largely invisible. Heat accumulates. Gases stratify. A base that feels fine at cycle 100 can already be doomed by decisions made at cycle 40, and the failure arrives as a slow suffocation rather than an event. That is why the ONI mid-game is the wall players talk about, and why the community leans so heavily on wikis and spreadsheets.

<cite index="104-1">ONI holds more than 120,000 player reviews at 96% positive and remains a pillar of the genre nearly six years after launch,</cite> so the difficulty is clearly not driving people away. It does mean the two games ask for different kinds of attention.

Which one has better characters?

RimWorld, and it is not close. Colonists have traits, skills, backstories, moods, phobias, relationships, marriages, and grudges, all of which interact with the survival systems to produce drama that nobody wrote. The AI storyteller deliberately paces crises against your prosperity, so the game is shaping a narrative arc rather than rolling dice.

Duplicants have personality in the Klei house style, which is charming, but they are closer to functional units with quirks than to characters with interiority. An ONI story is about a system failing. A RimWorld story is about a person.

If emergent narrative is specifically what you want from the genre, our guide to games with emergent storytelling covers what produces it.

Which one has better base building?

Different disciplines. RimWorld's base building is a two-dimensional layout puzzle: defence lanes, walk distances, temperature zones, and where the freezer goes relative to the kitchen. It is satisfying and it caps out at a manageable complexity.

ONI's base building is closer to plant engineering. You are routing gases, liquids, and power through a sealed volume where every machine produces heat that has to go somewhere, and the elegant solution to one problem creates the next. People post their ONI bases the way engineers post schematics.

If layout satisfaction is the appeal, ONI gives you more of it. If you want the layout to serve a story, RimWorld does.

Which one respects your time better?

RimWorld, in short sessions. A RimWorld colony can be picked up after two weeks away because the state of it is legible: look at the mood tab, look at the food, look at who is injured. The game tells you what it wants.

Oxygen Not Included punishes absence. Returning to a base after a break means reconstructing what past-you intended with the plumbing, and the answer is often buried in a heat problem you have to trace through three systems. It rewards continuous play and long sessions in a way RimWorld does not require.

That is a real consideration and it goes unmentioned in most comparisons. If your play time comes in ninety-minute pieces, RimWorld fits it better regardless of which premise appeals more.

Which one should you buy?

Buy RimWorld if you want to care about somebody. It is the better entry point to the genre, the better game for players coming from narrative games, and it has by far the larger mod ecosystem. Our is RimWorld worth it in 2026 covers the purchase decision including the DLC pricing problem.

Buy Oxygen Not Included if you want a problem. It is cheaper, it discounts constantly, its systems have more depth per hour, and it will absorb you completely if you are the kind of person who enjoys finding out why something is warm.

Buy ONI first if money matters, since the price gap is substantial and the base game is complete.

For the wider genre, best colony sim games covers the field, what is a colony sim explains the mechanics, and RimWorld vs Dwarf Fortress handles the other big head-to-head in the category.

A third option that leans toward the RimWorld side

Pappus sits closer to RimWorld than to ONI, since its interest is in characters rather than in physics. It is a space colony sim where the colonists are cats and you play the AI assigned to keep them alive, so the autonomous-agent relationship that produces RimWorld's stories is the whole design.

The cats have individual personalities and needs and enough independence to ignore your priorities, which is the RimWorld pawn relationship with the fiction made explicit. It shares ONI's sealed-environment survival framing and RimWorld's character-driven chaos, at a much smaller scope than either. There is a playable demo on its page that runs in your browser with nothing to install.

If you can only pick one of the two big ones this month: RimWorld for people, ONI for problems. Most players in the genre eventually own both.