Websocket

One websocket carries every live update. Public channels need no key.

wss://api.updown.fast/trade-api/ws/v1

Quick example

Node.js

import WebSocket from "ws";

const ws = new WebSocket("wss://api.updown.fast/trade-api/ws/v1");

ws.on("open", () => {
  ws.send(JSON.stringify({
    id: 1,
    cmd: "subscribe",
    params: { channels: ["orderbook_delta", "ticker"], series_tickers: ["sol-15m"] },
  }));
});

ws.on("message", (data) => console.log(JSON.parse(data)));

← {"id":1,"type":"subscribed","msg":{"channel":"orderbook_delta","sid":1}}
← {"id":1,"type":"subscribed","msg":{"channel":"ticker","sid":2}}
← {"type":"orderbook_snapshot","sid":1,"seq":1,"ts_ms":1791304746141,
   "msg":{"market_ticker":"sol-15m-261006-1630-1645","up":[["0.01","20"]],
          "down":[["0.95","20"],["0.94","23"],["0.92","26"]],"checksum":2742566057}}
← {"type":"ticker","sid":2,"seq":1,"ts_ms":1791304746141,
   "msg":{"market_ticker":"sol-15m-261006-1630-1645","up_bid":"0.01","up_bid_size":"20","up_ask":"0.05","up_ask_size":"20"}}
← {"type":"orderbook_delta","sid":1,"seq":2,"ts_ms":1791304747210,
   "msg":{"market_ticker":"sol-15m-261006-1630-1645","outcome":"down","price":"0.94","delta":"-3","checksum":2599747692}}

Commands

Every command carries an id you choose; the reply echoes it.

Command	Params	Reply
`subscribe`	`channels`, plus `market_tickers` and/or `series_tickers` (or `symbols` for `prices`)	One `subscribed` per channel, each with its `sid`.
`unsubscribe`	`sids`	One `unsubscribed` per sid.
`update_subscription`	`sid`, `action`: `add_markets` · `delete_markets` · `get_snapshot`, plus tickers or symbols	`ok`.
`list_subscriptions`	—	`ok` with `msg.subscriptions`.

Subscribe to a series, not a window, to follow it automatically. With series_tickers: ["sol-15m"], each new window’s window_lifecycle event and first orderbook_snapshot arrive on the same subscription — no resubscribing every 15 minutes. You can pass up to 100 tickers per command.

Channels

Channel	Keyed by	Sends
`orderbook_delta`	markets / series	An `orderbook_snapshot` per market, then one `orderbook_delta` per changed level.
`ticker`	markets / series	Top of book on the Up scale and the last trade price, when they change.
`trade`	markets / series	Every public trade (same shape as `GET /markets/{ticker}/trades`).
`window_lifecycle`	markets / series	A window’s events: `open` with its `price_to_beat`, then `closed`, then `settled` with `result` and `settlement_price`.
`prices`	`symbols`	Live price of an underlying: the current price at once, then every print.

Private channels (fill, user_orders, market_positions, balance) arrive with order entry; today they answer error 8 (AUTH_REQUIRED).

Prices

→ { "id": 2, "cmd": "subscribe", "params": { "channels": ["prices"], "symbols": ["X:BTCUSD", "AAPL"] } }
← { "type": "price", "sid": 3, "seq": 1, "ts_ms": 1791304719510,
    "msg": { "symbol": "X:BTCUSD", "price": "85587.91", "t_ms": 1791304719509 } }

Symbols are a stock (AAPL) or crypto (X:BTCUSD), upper case, up to 64 per command. t_ms is when the price printed at its source; ts_ms is when the server sent it. These are the same prices windows open and settle on.

Sequence numbers and recovery

Every data message has the envelope { type, sid, seq, ts_ms, msg }. seq starts at 1 and goes up by exactly 1 per message on that subscription.

If seq jumps, you missed messages. Send update_subscription with action: "get_snapshot" (or resubscribe) and drop your local books until fresh snapshots arrive.
Snapshots carry the whole book; deltas carry one level. A delta means: the contracts at price on outcome’s bid side change by delta. A level that reaches 0 is removed.

Checksums

Every orderbook_snapshot and orderbook_delta carries the checksum of the book after it is applied. Compute it on your side after each message; if it doesn’t match, your copy is wrong — request a snapshot.

Take each side’s levels best first (highest price first) and keep the top 10.
Write each level as price:count, exactly as sent on the wire: 0.55:10.
Join a side’s levels with ,, prefix them with up: and down:, and join the two sides with |: up:0.55:10,0.54:3|down:0.44:7 (an empty side is just up: or down:).
The checksum is the CRC-32 (the zlib / PNG one) of that string’s UTF-8 bytes, as an unsigned 32-bit integer.

import zlib

def checksum(up, down):
    side = lambda levels: ",".join(f"{p}:{n}" for p, n in levels[:10])
    return zlib.crc32(f"up:{side(up)}|down:{side(down)}".encode())

# up / down are lists of [price, count] strings, best first
assert checksum([["0.01", "20"]], [["0.95", "20"], ["0.94", "23"], ["0.92", "26"]]) == 2742566057

import { crc32 } from "node:zlib"; // Node 22+

const side = (levels) => levels.slice(0, 10).map(([p, n]) => `${p}:${n}`).join(",");
const checksum = (up, down) => crc32(`up:${side(up)}|down:${side(down)}`);

The REST orderbook returns the same checksum for the same book, so you can seed a book from REST and continue on the websocket.

Limits

Limit	Value
Connections per IP address	20
Subscriptions per connection	100
Commands per connection	10 per second, bursts of 20
Largest message you can send	64 KB

The server pings every 10 seconds; standard websocket clients answer automatically. A connection that stops answering is closed. Flooding commands closes the connection with code 1008, and a message over 64 KB with 1009. See Errors for the numbered error replies.

Trade API

Endpoints

Quick example

Commands

Channels

Prices

Sequence numbers and recovery

Checksums

Limits

​Quick example

​Commands

​Channels

​Prices

​Sequence numbers and recovery

​Checksums

​Limits

Quick example

Commands

Channels

Prices

Sequence numbers and recovery

Checksums

Limits