Kline (Candlestick)

Channel Name

spot:kline:{symbol}:{interval}

Authentication: not required (public channel).

Supported intervals: 1m, 5m, 15m, 1h, 4h, 1d. See Enums — K-line Intervals.

Description

Provides the latest candle as a snapshot on subscribe, then pushes a running OHLCV update after every fill that falls within the current candle's time window. There is no push at the window boundary — after a window ends, the next fill produces a push carrying the new candle's open_time. Subscribing to multiple intervals for the same symbol produces one push per interval per fill.

Send:

{ "type": "subscribe", "channel": "spot:kline:DFUSDT:1m" }

Response:

{ "type": "subscribed", "channel": "spot:kline:DFUSDT:1m" }

A spot_kline_snapshot is sent immediately after the ack.

Push Format

`spot_kline_snapshot`

Sent once on subscribe. Contains the latest completed or in-progress candle from the database.

{
  "type":    "spot_kline_snapshot",
  "channel": "spot:kline:DFUSDT:1m",
  "data": {
    "symbol":       "DFUSDT",
    "interval":     "1m",
    "open_time":    1778399940,
    "close_time":   1778399999,
    "open":         "0.4800",
    "high":         "0.5100",
    "low":          "0.4700",
    "close":        "0.5000",
    "volume":       "10000",
    "quote_volume": "4900",
    "trade_count":  234,
    "is_closed":    false
  }
}

`spot_kline_update`

Pushed after every fill that lands inside the current candle's window. The data format is identical to spot_kline_snapshot.

{
  "type":    "spot_kline_update",
  "channel": "spot:kline:DFUSDT:1m",
  "data": {
    "symbol":       "DFUSDT",
    "interval":     "1m",
    "open_time":    1778399940,
    "close_time":   1778399999,
    "open":         "0.4800",
    "high":         "0.5100",
    "low":          "0.4700",
    "close":        "0.5010",
    "volume":       "10030",
    "quote_volume": "4915",
    "trade_count":  235,
    "is_closed":    false
  }
}

is_closed is computed at the instant the frame is generated: it is true when now > close_time at push time. In practice a live per-fill update almost always carries is_closed: false (the fill just happened inside the window); is_closed: true appears mainly on the subscribe-time snapshot when the latest stored candle's window has already elapsed, or when a fill is persisted right at the window edge. Do not wait for an is_closed: true frame to close out a candle — treat a push with a newer open_time as the signal that the previous candle is final.

Field	Type	Description
`symbol`	string	Market identifier.
`interval`	string	Candle interval, e.g. `1m`.
`open_time`	integer	Candle open — unix seconds.
`close_time`	integer	Candle close — unix seconds. Equal to `open_time + interval_seconds − 1`.
`open`	string (decimal)	Opening price of the candle.
`high`	string (decimal)	Highest fill price so far in this candle.
`low`	string (decimal)	Lowest fill price so far in this candle.
`close`	string (decimal)	Most recent fill price in this candle.
`volume`	string (decimal)	Total base volume in this candle.
`quote_volume`	string (decimal)	Total quote volume in this candle.
`trade_count`	integer	Number of fills in this candle.
`is_closed`	boolean	Whether `now > close_time` at the moment the frame was generated. Not a boundary event — see above.

All timestamps are unix seconds.

Update Cadence

One spot_kline_update per fill that lands in the interval's time window.
Subscribing to 1m + 5m + 1h for the same symbol produces three pushes per fill (one per interval, each updating the respective candle).
No fixed polling timer — updates are purely event-driven.

Because each push replaces the running candle completely, a missed push is overwritten by the next one. No resync is needed. See Snapshot ↔ Live Sequencing.

Code Example

const ws = new WebSocket('wss://api.prex.world/ws');

// Local candle state keyed by interval
const candles = {};

ws.onopen = () => {
  ws.send(JSON.stringify({ type: 'subscribe', channel: 'spot:kline:DFUSDT:1m' }));
  ws.send(JSON.stringify({ type: 'subscribe', channel: 'spot:kline:DFUSDT:1h' }));
  setInterval(() => ws.send(JSON.stringify({ type: 'ping' })), 30000);
};

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);

  if (msg.type === 'spot_kline_snapshot' || msg.type === 'spot_kline_update') {
    const d = msg.data;

    const prev = candles[d.interval];
    if (prev && d.open_time > prev.open_time) {
      // A push with a newer open_time means the previous candle is final
      console.log(`[${d.interval}] Candle closed: O=${prev.open} H=${prev.high} L=${prev.low} C=${prev.close} V=${prev.volume}`);
      // Advance your chart to the next candle
    } else {
      console.log(`[${d.interval}] Live candle: C=${d.close} V=${d.volume}`);
      // Repaint the live (rightmost) bar on your chart
    }
    candles[d.interval] = d;
  }
};

Channel Name​

Description​

Subscribe​

Push Format​

spot_kline_snapshot​

spot_kline_update​

Update Cadence​

Code Example​