WebSocket API

Stream Reference

The Gemini WebSocket API provides real-time market data and account event streams:

L2 Order Book depth and tickers
Trade events and candles
Account-level orders and balance updates

Book Ticker

Schema	Frequency	Description
`{symbol}@bookTicker`	Real-time	Real time updates to the best bid/ask price for an order book.

Try Itbtcusd@bookTicker

disconnected


Code
{
  "u": 1751505576085,
  "E": 1751508438600117161,
  "s": "btcusd",
  "b": "45000.50",
  "B": "1.25000000",
  "a": "45001.00",
  "A": "0.75000000"
}

Field	Type	Description
`u`	number	Update ID
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`b`	string	Best bid price
`B`	string	Best bid quantity
`a`	string	Best ask price
`A`	string	Best ask quantity
`c`	string	Last trade price (present once the book has traded; omitted otherwise)
`C`	string	Last trade size (present once the book has traded; omitted otherwise)

L2 Partial Depth Streams

Schema	Frequency	Description
`{symbol}@depth5`	Periodic (1s)	Periodic snapshot of the top 5 levels once per second
`{symbol}@depth10`	Periodic (1s)	Top 10 levels
`{symbol}@depth20`	Periodic (1s)	Top 20 levels
`{symbol}@depth5@100ms`	Periodic (100ms)	Top 5 levels every 100 milliseconds
`{symbol}@depth10@100ms`	Periodic (100ms)	Top 10 levels
`{symbol}@depth20@100ms`	Periodic (100ms)	Top 20 levels

Try Itbtcusd@depth10@100ms

disconnected


Code
{
  "lastUpdateId": 12345678,
  "bids": [
    ["45000.50", "1.25000000"],
    ["45000.25", "0.50000000"]
  ],
  "asks": [
    ["45001.00", "0.75000000"],
    ["45001.25", "2.00000000"]
  ]
}

Field	Type	Description
`lastUpdateId`	number	Last update ID
`bids`	array	Array of [price, quantity]
`asks`	array	Array of [price, quantity]

L2 Differential Depth Streams

Schema	Frequency	Description
`{symbol}@depth`	Periodic (1s)	List of all changed price levels in the last second
`{symbol}@depth@100ms`	Periodic (100ms)	In the last 100 milliseconds

Try Itbtcusd@depth@100ms

disconnected

Initial Snapshot

Use the snapshot connection parameter to receive an initial orderbook snapshot when subscribing. Connect with wss://ws.gemini.com?snapshot=-1 for a full snapshot, or specify a positive number for top N levels.

Quantity zero indicates price level removal.


Code
{
  "e": "depthUpdate",
  "E": 1751508260659505382,
  "s": "btcusd",
  "U": 12345677,
  "u": 12345678,
  "b": [
    ["45000.50", "1.25000000"],
    ["45000.25", "0.00000000"]
  ],
  "a": [
    ["45001.00", "0.75000000"]
  ]
}

Field	Type	Description
`e`	string	Event type ("depthUpdate")
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`U`	number	First update ID in this event
`u`	number	Last update ID in this event
`b`	array	Bid updates [price, quantity]
`a`	array	Ask updates [price, quantity]

Trade Stream

Schema	Frequency	Description
`{symbol}@trade`	Real-time	Real time trade executions

Try Itbtcusd@trade

disconnected


Code
{
  "E": 1759873803503023900,
  "s": "btcusd",
  "t": 2840140956529623,
  "p": "120649.97000",
  "q": "0.0046190900",
  "m": true
}

Field	Type	Description
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`t`	number	Trade ID
`p`	string	Price
`q`	string	Quantity
`m`	boolean	Is buyer the maker

Order Events

Requires an authenticated session

Schema	Frequency	Description
`orders@account`	Real-time	Real time order activity for the account associated with the authenticated API key
`orders@session`	Real-time	Real time order activity for the authenticated API key


Code
# Order Event - New
{
  "e":"orderUpdate",
  "E":1759291847686856569,
  "s":"BTCUSD",
  "i":73797746498585286,
  "c":"my-order-1759291847503",
  "S":"BUY",
  "o":"LIMIT",
  "X":"NEW",
  "p":"1.00000",
  "q":"0.0000100000",
  "z":"0.0000100000",
  "T":1759291847686856569
}

# Order Event - Canceled
{
  "e":"orderUpdate",
  "E":1759291847731455006,
  "s":"BTCUSD",
  "i":73797746498585286,
  "c":"my-order-1759291847503",
  "X":"CANCELED",
  "T":1759291847731455006
}

Field	Type	Description
`e`	string	Event type (`orderUpdate`)
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`i`	number	Order ID
`c`	string	Client order ID. For RFQ maker fills, this is the `clientId` supplied to `rfq.submit_quote`, or Gemini's deterministic RFQ client order ID when omitted.
`S`	string	Side, `BUY / SELL`
`o`	string	Type, `LIMIT / MARKET / STOP_LIMIT / STOP_MARKET`
`X`	string	Status, `NEW / OPEN / FILLED / PARTIALLY_FILLED / CANCELED / REJECTED / MODIFIED`
`p`	string	Order price
`P`	string	Stop price (`0` when not a stop order)
`q`	string	Original quantity
`z`	string	Remaining quantity
`Z`	string	Executed quantity. For `FILLED` / `PARTIALLY_FILLED` events, this is the quantity filled in the last execution. For `CANCELED` and other events, this is the cumulative quantity filled over the lifetime of the order. Use `Z` (not the order status) to determine how much filled — e.g. a fully-filled `IOC` terminates as `CANCELED`.
`L`	string	Last execution price
`t`	number	Trade ID
`n`	string	Fee amount (only present in 'FILLED' events)
`m`	boolean	Maker flag on fills: `true` = maker, `false` = taker (present on fills only)
`r`	string	Rejection reason
`T`	number	Update time (nanoseconds)
`O`	string	Event outcome for event contracts, `YES / NO`

Fields with empty or zero values may be omitted from the event.

Post-only and immediate time-in-force orders are accepted, then cancelled — they are never REJECTED:

MOC (maker-or-cancel / post-only): if it would take liquidity, the order is cancelled with MakerOrCancelWouldTake and never fills.
IOC (immediate-or-cancel): fills whatever crosses immediately, then cancels the remainder with ImmediateOrCancelWouldPost. A fully-filled IOC still ends with a CANCELED event — so determine what filled from the executed quantity (Z), never from the final order status.
FOK (fill-or-kill): fills completely and immediately, or is cancelled in full with FillOrKillWouldNotFill (no partial fills).

order.place for these still returns a 200 response with an initial NEW; a true rejection returns a non-200 status with an error code.

Rejection Reasons

When an order is REJECTED, the r field contains one of:

Reason	Description
`MarketNotOpen`	Market is closed or paused
`InsufficientFunds`	Account lacks sufficient balance
`InvalidPrice`	Price violates constraints
`LimitPriceOffTick`	Price does not align with tick size
`InvalidQuantity`	Quantity below minimum or off increment
`InvalidStopPrice`	Stop price violates constraints
`InvalidTotalSpend`	Total spend calculation error
`DuplicateOrder`	Duplicate client order ID
`InsufficientLiquidity`	Not enough liquidity at price
`UnknownInstrument`	Trading pair does not exist

Cancellation Reasons

When an order is CANCELED by the system, the r field contains one of:

Reason	Description
`SelfCrossPrevented`	Self-trade prevention triggered
`FillOrKillWouldNotFill`	FOK order could not fill completely
`ImmediateOrCancelWouldPost`	IOC order would post to book
`MakerOrCancelWouldTake`	MOC order would take liquidity
`AuctionCancelled`	Auction-related cancellation
`ExceedsPriceLimits`	Price moved beyond limits

Balance Updates

Requires an authenticated session

Schema	Frequency	Description
`balances@account`	Real-time	Real time balance updates for the account associated with the authenticated API key
`balances@account@1s`	Periodic (1s)	Periodic snapshot of all balances every second for the account associated with the authenticated API key

The balances@account stream pushes updates in real time whenever a balance change occurs, and only includes the assets that changed. The balances@account@1s stream sends a complete snapshot of all account balances every second, regardless of whether they changed. On subscribe, balances@account@1s will immediately send the current balances if available.


Code
# Balance Update
{
  "e": "balanceUpdate",
  "E": 1768250434780000000,
  "u": 1768250421600000000,
  "B": [
    {
      "a": "USD",
      "f": "207.39",
      "c": "207.39"
    }
  ]
}

Field	Type	Description
`e`	string	Event type ("balanceUpdate")
`E`	number	Event time (nanoseconds)
`u`	number	Time of the last account update (nanoseconds)
`B`	array	Balance updates
`a`	string	Asset code
`f`	string	Available balance (amount available to trade)
`c`	string	Confirmed balance (total balance including pending)

Contract Status

Prediction-market contract lifecycle events — status transitions (e.g. Awaiting Approval → Approved → Active) and strike-populated moments for Up/Down contracts.

Schema	Frequency	Description
`contractStatus`	Real-time	Status changes and strike-price updates for prediction-market contracts


Code
# Strike-based contract (e.g. HI78999D63)
{
  "e": "contractStatus",
  "E": 1776871540195,
  "s": "gemi-btc15m2604221545-hi78999d63",
  "k": "btc15m2604221545",
  "c": "HI78999D63",
  "i": 134794,
  "p": "78999.63",
  "o": "Awaiting Approval",
  "n": "Approved"
}

# Up/Down contract (no numeric strike — `p` omitted until populated)
{
  "e": "contractStatus",
  "E": 1776871295498,
  "s": "gemi-btc05m2604221630-up",
  "k": "btc05m2604221630",
  "c": "UP",
  "i": 134791,
  "o": "Awaiting Approval",
  "n": "Approved"
}

Field	Type	Description
`e`	string	Event type (`contractStatus`)
`E`	number	Event time (Unix milliseconds)
`s`	string	Instrument symbol
`k`	string	Event ticker
`c`	string	Contract ticker (e.g. `HI78999D63`, `UP`, `DOWN`)
`i`	number	Contract ID
`p`	string	Strike price parsed from the contract ticker. Omitted for Up/Down contracts until the strike is set at activation
`o`	string	Previous status
`n`	string	New status

For Up/Down contracts, p is omitted while the strike is unknown and included once it is set — subscribers can detect strike availability by the field's presence.

Message Format FIX API

WebSocket API

Stream Reference

The Gemini WebSocket API provides real-time market data and account event streams:

L2 Order Book depth and tickers
Trade events and candles
Account-level orders and balance updates

Book Ticker

Schema	Frequency	Description
`{symbol}@bookTicker`	Real-time	Real time updates to the best bid/ask price for an order book.

Try Itbtcusd@bookTicker

disconnected


Code
{
  "u": 1751505576085,
  "E": 1751508438600117161,
  "s": "btcusd",
  "b": "45000.50",
  "B": "1.25000000",
  "a": "45001.00",
  "A": "0.75000000"
}

Field	Type	Description
`u`	number	Update ID
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`b`	string	Best bid price
`B`	string	Best bid quantity
`a`	string	Best ask price
`A`	string	Best ask quantity
`c`	string	Last trade price (present once the book has traded; omitted otherwise)
`C`	string	Last trade size (present once the book has traded; omitted otherwise)

L2 Partial Depth Streams

Schema	Frequency	Description
`{symbol}@depth5`	Periodic (1s)	Periodic snapshot of the top 5 levels once per second
`{symbol}@depth10`	Periodic (1s)	Top 10 levels
`{symbol}@depth20`	Periodic (1s)	Top 20 levels
`{symbol}@depth5@100ms`	Periodic (100ms)	Top 5 levels every 100 milliseconds
`{symbol}@depth10@100ms`	Periodic (100ms)	Top 10 levels
`{symbol}@depth20@100ms`	Periodic (100ms)	Top 20 levels

Try Itbtcusd@depth10@100ms

disconnected


Code
{
  "lastUpdateId": 12345678,
  "bids": [
    ["45000.50", "1.25000000"],
    ["45000.25", "0.50000000"]
  ],
  "asks": [
    ["45001.00", "0.75000000"],
    ["45001.25", "2.00000000"]
  ]
}

Field	Type	Description
`lastUpdateId`	number	Last update ID
`bids`	array	Array of [price, quantity]
`asks`	array	Array of [price, quantity]

L2 Differential Depth Streams

Schema	Frequency	Description
`{symbol}@depth`	Periodic (1s)	List of all changed price levels in the last second
`{symbol}@depth@100ms`	Periodic (100ms)	In the last 100 milliseconds

Try Itbtcusd@depth@100ms

disconnected

Initial Snapshot

Quantity zero indicates price level removal.


Code
{
  "e": "depthUpdate",
  "E": 1751508260659505382,
  "s": "btcusd",
  "U": 12345677,
  "u": 12345678,
  "b": [
    ["45000.50", "1.25000000"],
    ["45000.25", "0.00000000"]
  ],
  "a": [
    ["45001.00", "0.75000000"]
  ]
}

Field	Type	Description
`e`	string	Event type ("depthUpdate")
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`U`	number	First update ID in this event
`u`	number	Last update ID in this event
`b`	array	Bid updates [price, quantity]
`a`	array	Ask updates [price, quantity]

Trade Stream

Schema	Frequency	Description
`{symbol}@trade`	Real-time	Real time trade executions

Try Itbtcusd@trade

disconnected


Code
{
  "E": 1759873803503023900,
  "s": "btcusd",
  "t": 2840140956529623,
  "p": "120649.97000",
  "q": "0.0046190900",
  "m": true
}

Field	Type	Description
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`t`	number	Trade ID
`p`	string	Price
`q`	string	Quantity
`m`	boolean	Is buyer the maker

Order Events

Requires an authenticated session

Schema	Frequency	Description
`orders@account`	Real-time	Real time order activity for the account associated with the authenticated API key
`orders@session`	Real-time	Real time order activity for the authenticated API key


Code
# Order Event - New
{
  "e":"orderUpdate",
  "E":1759291847686856569,
  "s":"BTCUSD",
  "i":73797746498585286,
  "c":"my-order-1759291847503",
  "S":"BUY",
  "o":"LIMIT",
  "X":"NEW",
  "p":"1.00000",
  "q":"0.0000100000",
  "z":"0.0000100000",
  "T":1759291847686856569
}

# Order Event - Canceled
{
  "e":"orderUpdate",
  "E":1759291847731455006,
  "s":"BTCUSD",
  "i":73797746498585286,
  "c":"my-order-1759291847503",
  "X":"CANCELED",
  "T":1759291847731455006
}

Field	Type	Description
`e`	string	Event type (`orderUpdate`)
`E`	number	Event time (nanoseconds)
`s`	string	Symbol
`i`	number	Order ID
`c`	string	Client order ID. For RFQ maker fills, this is the `clientId` supplied to `rfq.submit_quote`, or Gemini's deterministic RFQ client order ID when omitted.
`S`	string	Side, `BUY / SELL`
`o`	string	Type, `LIMIT / MARKET / STOP_LIMIT / STOP_MARKET`
`X`	string	Status, `NEW / OPEN / FILLED / PARTIALLY_FILLED / CANCELED / REJECTED / MODIFIED`
`p`	string	Order price
`P`	string	Stop price (`0` when not a stop order)
`q`	string	Original quantity
`z`	string	Remaining quantity
`Z`	string	Executed quantity. For `FILLED` / `PARTIALLY_FILLED` events, this is the quantity filled in the last execution. For `CANCELED` and other events, this is the cumulative quantity filled over the lifetime of the order. Use `Z` (not the order status) to determine how much filled — e.g. a fully-filled `IOC` terminates as `CANCELED`.
`L`	string	Last execution price
`t`	number	Trade ID
`n`	string	Fee amount (only present in 'FILLED' events)
`m`	boolean	Maker flag on fills: `true` = maker, `false` = taker (present on fills only)
`r`	string	Rejection reason
`T`	number	Update time (nanoseconds)
`O`	string	Event outcome for event contracts, `YES / NO`

Fields with empty or zero values may be omitted from the event.

Post-only and immediate time-in-force orders are accepted, then cancelled — they are never REJECTED:

MOC (maker-or-cancel / post-only): if it would take liquidity, the order is cancelled with MakerOrCancelWouldTake and never fills.
IOC (immediate-or-cancel): fills whatever crosses immediately, then cancels the remainder with ImmediateOrCancelWouldPost. A fully-filled IOC still ends with a CANCELED event — so determine what filled from the executed quantity (Z), never from the final order status.
FOK (fill-or-kill): fills completely and immediately, or is cancelled in full with FillOrKillWouldNotFill (no partial fills).

order.place for these still returns a 200 response with an initial NEW; a true rejection returns a non-200 status with an error code.

Rejection Reasons

When an order is REJECTED, the r field contains one of:

Reason	Description
`MarketNotOpen`	Market is closed or paused
`InsufficientFunds`	Account lacks sufficient balance
`InvalidPrice`	Price violates constraints
`LimitPriceOffTick`	Price does not align with tick size
`InvalidQuantity`	Quantity below minimum or off increment
`InvalidStopPrice`	Stop price violates constraints
`InvalidTotalSpend`	Total spend calculation error
`DuplicateOrder`	Duplicate client order ID
`InsufficientLiquidity`	Not enough liquidity at price
`UnknownInstrument`	Trading pair does not exist

Cancellation Reasons

When an order is CANCELED by the system, the r field contains one of:

Reason	Description
`SelfCrossPrevented`	Self-trade prevention triggered
`FillOrKillWouldNotFill`	FOK order could not fill completely
`ImmediateOrCancelWouldPost`	IOC order would post to book
`MakerOrCancelWouldTake`	MOC order would take liquidity
`AuctionCancelled`	Auction-related cancellation
`ExceedsPriceLimits`	Price moved beyond limits

Balance Updates

Requires an authenticated session

Schema	Frequency	Description
`balances@account`	Real-time	Real time balance updates for the account associated with the authenticated API key
`balances@account@1s`	Periodic (1s)	Periodic snapshot of all balances every second for the account associated with the authenticated API key


Code
# Balance Update
{
  "e": "balanceUpdate",
  "E": 1768250434780000000,
  "u": 1768250421600000000,
  "B": [
    {
      "a": "USD",
      "f": "207.39",
      "c": "207.39"
    }
  ]
}

Field	Type	Description
`e`	string	Event type ("balanceUpdate")
`E`	number	Event time (nanoseconds)
`u`	number	Time of the last account update (nanoseconds)
`B`	array	Balance updates
`a`	string	Asset code
`f`	string	Available balance (amount available to trade)
`c`	string	Confirmed balance (total balance including pending)

Contract Status

Prediction-market contract lifecycle events — status transitions (e.g. Awaiting Approval → Approved → Active) and strike-populated moments for Up/Down contracts.

Schema	Frequency	Description
`contractStatus`	Real-time	Status changes and strike-price updates for prediction-market contracts


Code
# Strike-based contract (e.g. HI78999D63)
{
  "e": "contractStatus",
  "E": 1776871540195,
  "s": "gemi-btc15m2604221545-hi78999d63",
  "k": "btc15m2604221545",
  "c": "HI78999D63",
  "i": 134794,
  "p": "78999.63",
  "o": "Awaiting Approval",
  "n": "Approved"
}

# Up/Down contract (no numeric strike — `p` omitted until populated)
{
  "e": "contractStatus",
  "E": 1776871295498,
  "s": "gemi-btc05m2604221630-up",
  "k": "btc05m2604221630",
  "c": "UP",
  "i": 134791,
  "o": "Awaiting Approval",
  "n": "Approved"
}

Field	Type	Description
`e`	string	Event type (`contractStatus`)
`E`	number	Event time (Unix milliseconds)
`s`	string	Instrument symbol
`k`	string	Event ticker
`c`	string	Contract ticker (e.g. `HI78999D63`, `UP`, `DOWN`)
`i`	number	Contract ID
`p`	string	Strike price parsed from the contract ticker. Omitted for Up/Down contracts until the strike is set at activation
`o`	string	Previous status
`n`	string	New status

For Up/Down contracts, p is omitted while the strike is unknown and included once it is set — subscribers can detect strike availability by the field's presence.

Message Format FIX API