WebSockets API

This reference documents the Paxos WebSocket API.

The Market Data Feed streams event-driven updates for the entire order book or for a single market. The Execution Data Feed streams event information for all markets or for a single market.

⚙️ Follow the quickstart for a hands-on introduction.

Market Data Feed

Once a secure (wss://) connection is established, the initial response message shows the state of the order book, including both bids and asks, in the SNAPSHOT. Prices are in descending order for bids and ascending order for asks.

tip

When streaming data for all markets, differentiate the per-market updates using the market field.

Market Data Request

• Production: wss://ws.paxos.com/marketdata
• Sandbox: wss://ws.sandbox.paxos.com/marketdata

Market Data Path Parameter

• Production: wss://ws.paxos.com/marketdata/{market}
• Sandbox: wss://ws.sandbox.paxos.com/marketdata/{market}

Parameter	Required	Description
market	No	Filter the data stream for a single market. For example, BTCUSD or another market from available markets.

Market Data Initial Response

Parameter	Required	Description
type	Yes	The initial value of SNAPSHOT shows the state of the order book for both bids and asks. Subsequent messages show all executed trades, and other order book changes, in the UPDATE stream.
market	Yes	One of the available markets or a single market if the market path parameter is specified.
bids	Yes	Includes bids.price in descending order and bids.amount. Each price-amount pair represents a level of the book.
asks	Yes	Includes asks.price in ascending order and asks.amount. Each price-amount pair represents a level of the book.
final_snapshot	Yes	Demarcates the end of the initial SNAPSHOT. Initial value always true. Subsequent messages in UPDATE format.

Market Data Update Response

When processing UPDATE messages observe the following rules:

• If side=BUY and amount=0, remove the existing entry with price price from the bids list.
• If side=BUY and an entry with price price already exists in the bids list, update the amount for the given entry in the bids list to amount.
• If side=BUY and no entry with price price exists in the bids list, add an entry with price price and amount amount to bids list.
• If side=SELL, apply the logic used as for BUY to the asks list.

Parameter	Required	Description
type	Yes	Value always UPDATE. Show all executed trades, and other order book changes, in the data stream.
market	Yes	One of the available markets or the single market if the market path parameter is specified.
side	Yes	Value either BUY or SELL. Specifies the activity type.
price	Yes	The current price.
amount	Yes	The current amount.

Market Data Example Response

Request URL: wss://ws.sandbox.paxos.com/marketdata/BTCUSD

{
  "type": "SNAPSHOT",
  "market": "BTCUSD",
  "bids": [
    {
      "price": "19994.25",
      "amount": "0.7755"
    },
    {
      "price": "19993.75",
      "amount": "0.83676985"
    },
    ...
  ],
  "asks": [
    {
      "price": "19994.5",
      "amount": "0.97548541"
    },
    {
      "price": "19996",
      "amount": "1.135"
    },
    ...
  ],
  "final_snapshot": true
}

{
  "type": "UPDATE",
  "market": "BTCUSD",
  "side": "BUY",
  "price": "19958.5",
  "amount": "0.62649999"
}

{
  "type": "UPDATE",
  "market": "BTCUSD",
  "side": "SELL",
  "price": "20115.25",
  "amount": "0"
}
...

Execution Data Feed

Upon secure (wss://) connection, you will start to receive messages for each market execution (based on the use of the market parameter). The first message corresponds to the last execution for the market at the point of the connection. After that, each new message represents a new execution.

If there are no executions for longer periods of time for a particular market upon connection you may not receive any message until a new execution is made.

tip

Upon reconnection you will receive the last execution for the market, in which case clients should handle duplicate messages. You may use a match number as an idempotent field.

Execution Data Request

• Production: wss://ws.paxos.com/executiondata
• Sandbox: wss://ws.sandbox.paxos.com/executiondata

Execution Data Path Parameter

• Production: wss://ws.paxos.com/executiondata/{market}
• Sandbox: wss://ws.sandbox.paxos.com/executiondata/{market}

Parameter	Required	Description
market	No	Filter the data stream for a single market. For example, BTCUSD or another market from available markets.

Execution Data Response

Parameter	Required	Description
market	Yes	One of the available markets or the single market if the market path parameter is specified.
price	Yes	The execution price.
amount	Yes	The execution amount.
executed_at	Yes	Timestamp of the execution.
match_number	Yes	Unique execution number.

Execution Data Example Response

Request URL: wss://ws.sandbox.paxos.com/executiondata/BTCUSD

{
  "market": "BTCUSD",
  "price": "24228.75",
  "amount": "0.00000412",
  "executed_at": "2023-03-13T18:46:53.386Z",
  "match_number": "6AJVAX7BTCH8"
}
...

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