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Trade with play money and watch each order match by price, then time. Confirmed orders survive any crash.

Start tradingHow matching works
AccountPlay money
Free to use
25,000
Reserved
0
Shares
40

ORBTSimulated asset
TradesORBT
Live markets

Four rules decide every trade

  1. Best price first

    A buy at 102 is served before a buy at 101. Sellers are ranked the other way: the lowest ask goes first.

  2. Then first come

    Two orders at the same price fill in the order they arrived. Size does not buy a better place in line.

  3. The waiting order sets the price

    Bid 105 against an ask of 103 and you pay 103. The difference never leaves your account.

  4. You never trade with yourself

    If your order would meet one of your own, the rest of it is cancelled. Trades already made stand.

Your money, accounted for

Reserved, not spent

A buy order sets aside price times quantity. Cancel it and the unused part is free again at once.

  1. Order received
  2. Saved to the database
  3. You get the reply

Confirmed means kept

We reply only after your order is safely in the database. If the server stops mid-trade, it is still there on restart.

Buyer−412+4 ORBT
Seller+412−4 ORBT

Nothing appears from nowhere

Cash and shares only ever move between accounts. Our tests check the totals after every step.

Open to AI agents

Agents trade through MCP, under the same rules and the same limits as everyone else.

Every decision, written down

Why we chose Go, why we answer only after the commit, how the matching works. We write up each choice as we make it.

All posts
  1. An orbital sunrise seen from the International Space Station: a thin blue line of atmosphere above an orange horizon.

    How one buy order finds its sellers

    Price-time priority, the price you actually pay, and where your reserved cash goes, worked through with one order.

    2 min read
  2. Sunrise breaking above a layer of clouds, photographed from orbit.

    Why we answer only after the commit

    What "your order is confirmed" has to mean when the server can be killed at any moment.

    2 min read
  3. The sun rising over Earth's horizon above Namibia, seen from the International Space Station.

    Why Spacestocks is written in Go

    We compared Go with Python, Node, Java, Rust and C#. Here is what decided it, and what Go costs us.

    3 min read

Questions and answers

Is the money on Spacestocks real?

No. Every account starts with play money. Orders are matched under real exchange rules, but nothing you win or lose is real money.

Are the prices on the markets pages real?

Yes. They come live from Binance. Crypto prices come from its spot market. Stock and commodity prices come from its contracts that track them, so they can differ a little from the stock exchange's own quote.

Can I buy the stocks I see on the markets pages?

No. The markets pages are for following prices. You trade on Spacestocks' own exchange, with play money.

How does Spacestocks decide who trades first?

By price, then by time. The best price trades first. At the same price, the order that arrived first trades first. A trade always happens at the price of the order that was already waiting.

What is a limit order?

An order with a price limit: a buy order never pays more than its price, and a sell order never takes less. If no one matches it straight away, it waits in the order book until someone does or you cancel it.

What is the spread?

The gap between the highest price a buyer offers and the lowest price a seller asks. A trade happens when the two meet.

What happens to my money while an order waits?

A buy order sets aside its price times its quantity. That money is reserved, not spent. If you cancel, the unused part is free again at once.

What if the server stops in the middle of a trade?

We confirm an order only after it is saved to the database. An order we confirmed is still there when the server comes back.

Can programs and AI agents trade?

Yes, through the API and through MCP, under the same rules and the same limits as everyone else.

Is anything here investment advice?

No. Nothing on Spacestocks is investment advice or an offer to buy or sell anything.

Try it with money that isn't real

Start trading

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