Alliances let players band together for mutual benefit. Up to 6 players can be in an alliance at once.
Every member earns a per-planet science output bonus on all planets they own. It's calculated individually per member and combines two factors:
1. Base bonus — rewards smaller empires.
Larger empires get less bonus, capping at 0% once you control 50% of the galaxy population (the solo-win threshold):
base% = max(0, (1 − 2 × popShare) × 40)
where popShare = your total population ÷ sum of every non-eliminated player's population.
| Galaxy population share | Base |
|---|---|
| 0% | 40% |
| 10% | 32% |
| 25% | 20% |
| 40% | 8% |
| 50% or more | 0% |
2. Member-count multiplier — rewards bigger alliances.
The base is then multiplied by a factor that grows with the alliance size:
| Members | Multiplier |
|---|---|
| 1 | 0% |
| 2 | 20% |
| 3 | 40% |
| 4 | 60% |
| 5 | 80% |
| 6 | 100% |
Final bonus = base × member multiplier. So a small empire (popShare 10%, base 32%) in a full 6-member alliance gets +32% science on every planet they own. The same player in a 3-member alliance gets +12.8%.
Defeated players (0 population) get no bonus and are dropped from the denominator — their fall actually raises the base for everyone still standing.
You can see your own breakdown on the Alliance → Research tab, and on the per-planet science tooltip.
The 70% alliance population threshold is itself an alliance benefit: after day 500, an alliance with at least 2 members whose combined population is 70% or more of the galaxy total wins the game outright. See How to win for the full ruleset and how it interacts with the solo 50% threshold.
Members automatically share planet ownership data with each other, helping keep everyone's map up to date. See Fog of War.
Information collected by any member on another empire (planet count, ship count, current research) is automatically shared with all alliance members.
Creating an alliance automatically opens a private group chat for its members.
Members of the same alliance are treated as allies — they cannot attack each other. If anyone declares war on an alliance member, the other members lose their ranked-combat protection against the attacker, allowing them to retaliate regardless of rank difference. See Diplomacy for the full ranked-combat rules.
A member can leave at any time. The alliance science bonus stops on the next week (membership change invalidates the cached bonus immediately, and per-planet science recomputes for everyone affected). The leaver's diplomatic state with former alliance members drops to Neutral.