How does cryptsy.com allocate trades for many orders with same price ?

Orders can come from one or many accounts, my question applies to both situations, but it's obviously more interesting how they are executed when orders come from multiple accounts from different people. For example, if I see order for 100 BTC and want to attach my order for 0.1 BTC to the same price tag, what are my chances of getting a deal ? Do I get a deal only after all 100BTC exchanged ?

Obvously my question applies to both types: buy and sell orders.

Do other exchanges have same order allocation schema as Cryptsy ? If not, what allocation schemas do they use ?

Examples of possible allocations that I can think of:

1) First Come First Serve - earliest order gets deal first

2) Last Come First Serve - latest order gets deal first

3) Proportional - deal amount is distributed between orders proportional to amount of these orders.

4) Minimal split - system picks closest amount to avoid splitting orders into many small fractions.

5) Small orders first, Large Last - close as many orders as possible to keep minimum number of open orders in the system.

6) Each account gets equal share from new deal regardless of order size or time

7) Random per account - equal probability for each participating account to get a deal

8) Random per order - gives incentive to make many smaller orders rather than one large order

  • possible duplicate of How do buy and sell orders work?
    – dchapes
    Mar 31, 2014 at 4:53
  • No exchange could ever use #2, it'd give an unfair advantage to those entering at last minute - high frequency trading only, no humans allowed! Numbers 3, 7 and 8 would still favor last-minute traders, though less than #2. #4 or 6 seem to me the only ones to be fair appart from #1
    – Joe Pineda
    Mar 31, 2014 at 18:35
  • While I have done no research whatsoever to prove it, I am pretty sure that only FIFO, 1) is used. Everything else is way more complicated and/or easy to game.
    – Murch
    Apr 1, 2014 at 13:05

2 Answers 2


At Cryptsy the order is First In First Out influenced by the account's trading history. If the server were to receive buy orders at the same time assuming there is enough coins at the specified price to fill the orders, the server looks at each account and the one with the most trading history gets processed first, then in order to the account with the least trading history. I work for Cryptsy, I'm Brad!


According to this answer it allocates according to rule #1 - First Some First Serve.

  • So much "First Come, First Served", actually, that occassionally I've placed a buy order some satoshis below the topmost sell price and get it served with 2 different events at 2 prices, even though the total amount of coins offered at top sell price has not been depleted.
    – Joe Pineda
    Mar 31, 2014 at 18:41

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