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The candle channel delivers live OHLCV updates for a contract at a specified interval. The current open bar is pushed on change, throttled to roughly every 100 ms (at most ten frames per second). When a bar closes at an interval boundary, the server pushes the finalized closed bar (with "closed": true) immediately followed by the first update for the new open bar — so your chart never misses a transition. The subscription opens with a snapshot frame of recent bars, so a chart can be drawn from the stream alone.

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Subscribing

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string
required
The numeric contract ID to receive candles for.
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string
required
The candle interval. Accepts the same values as the candleSnapshot REST endpoint: 1m, 3m, 5m, 15m, 30m, 1h, 2h, 4h, 8h, 12h, 1d, 3d, 1w, 1M.

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Push message format

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Field reference

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number
Server send timestamp in Unix milliseconds.
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string
Contract ID. Matches the asset value in your subscription.
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string
Interval of this candle (e.g., "1m").
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number
Bar open time — Unix milliseconds at the start of this interval bucket.
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number
Bar close time — Unix milliseconds at the end of this interval bucket (exclusive).
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string
Open price of the bar (raw string). This is the price of the first trade in the interval.
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string
Highest trade price within the bar (raw string).
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string
Lowest trade price within the bar (raw string).
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string
Close price of the bar (raw string). For an open bar, this is the price of the most recent trade so far.
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string
Total traded volume within the bar (raw string).
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number
Number of individual trades that make up this bar.
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boolean
false for an in-progress open bar. true for a finalized closed bar — this message is pushed exactly once at the interval boundary and will not be updated further.

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Snapshot on subscribe

On a successful subscription the server first pushes a snapshot frame marked "isSnapshot": true. Its data is shaped differently from an incremental frame — an object containing roughly the last 300 closed bars plus the current open bar, in ascending time order:
Incremental frames that follow carry no isSnapshot and a single bar in data. When no data exists yet, the snapshot frame carries "data": {}.

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Initialising a chart

1

Subscribe and render the snapshot

The first frame is the snapshot described above. Render its candles array as the initial chart state — no REST call is required for a standard chart window.
2

Merge increments on bar open time (t)

Subsequent frames carry one bar each. Key on data.t: update the bar with a matching t, or append a new one.
3

Handle closed-bar events

A message with "closed": true finalizes that bar. The next message carries the new open bar with a later t.
4

Fetch longer history via REST

For a window deeper than the snapshot, call candleSnapshot.
Do not rely on the incremental stream to fill a quiet period. While the exchange is running, an interval with no trades is backfilled with a flat bar (v of 0) so the axis stays continuous — but after a long gap with no trades, only the most recent flat bar is pushed, not each one in between. Those bars are still stored: re-subscribe to take a fresh snapshot, or call candleSnapshot.
Do not assume the time axis has no holes. Intervals that elapse while a node is restarting or stopped are not backfilled, leaving a permanent gap in history. Render missing ranges as “no data” — prices and volumes elsewhere remain correct.
An open bar is pushed only when it changes. If no trade has occurred since the last push, the same values are not re-sent.
You can subscribe to multiple intervals for the same asset simultaneously — for example, 1m and 1h — each as a separate subscription. They operate independently and do not interfere with each other.
All price and volume values are raw strings. Apply the contract’s decimal precision before rendering values on a chart.