BBO (Best Bid/Offer) - Top of Book

Stream the best bid and best ask for any trading pair with minimal bandwidth, ideal for price tracking, execution triggers, and spread monitoring.

How to Subscribe

Send a subscription message to the WebSocket endpoint:

{
  "method": "subscribe",
  "subscription": {
    "type": "bbo",
    "coin": "BTC"
  }
}

Subscription Parameters

Coin Format by Market Type

The coin field accepts different formats depending on the market:

Subscription Examples

{
  "method": "subscribe",
  "subscription": {
    "type": "bbo",
    "coin": "BTC"
  }
}

encoding = 10 * outcome + side

The first websocket message after subscribing is a subscriptionResponse; subsequent messages carry the bbo payloads.

Response Field Reference

{
  "channel": "bbo",
  "data": {
    "coin": "BTC",
    "time": 1751427259657,
    "bbo": [
      {"px": "106217.0", "sz": "0.001", "n": 1},
      {"px": "106233.0", "sz": "0.26739", "n": 3}
    ]
  }
}

Level Object Fields

{"channel": "bbo", "data": {"coin": "BTC", "time": 1751427259657, "bbo": [{"px": "106217.0", "sz": "0.001", "n": 1}, null]}}

Semantics

• On-change only: a message is sent only when the top bid or ask changes (price, size, or order count). Identical top-of-book across blocks is suppressed.
• Snapshot-based: like l2Book, bbo is computed from the per-block snapshot, not an incremental stream. A dropped broadcast recovers on the next snapshot, so a lagging client is not torn down (unlike trades/l4Book).
• Timestamp: time is the snapshot's block time in milliseconds.
• Outcome markets: for HIP-4 outcome coins, the top-of-book reflects the merged two-sided book (the 1 - p counterpart is folded in), consistent with l2Book.

Dwellir BBO vs Public Hyperliquid BBO

Dwellir's bbo subscription mirrors the public Hyperliquid bbo WebSocket channel: the same subscribe message and the same {"channel": "bbo", "data": {"coin", "time", "bbo": [bid, ask]}} payload shape. Clients written against the public feed work unchanged.

The difference is delivery, not data: Dwellir's bbo is snapshot-based and deduped (emitted only when top-of-book changes, at most once per block), so a lagging client recovers on the next snapshot instead of being torn down.

Aggregated Alternative: l2Book with nLevels=1

The native bbo subscription always serves raw top-of-book. When you instead want rounded or aggregated top-of-book (for example to reduce update frequency, or to keep a single unified l2Book payload shape across all depths), subscribe to l2Book with nLevels=1 and the desired nSigFigs:

{
  "method": "subscribe",
  "subscription": {
    "type": "l2Book",
    "coin": "BTC",
    "nSigFigs": 5,
    "nLevels": 1
  }
}

This returns exactly one bid and one ask level in the standard l2Book levels: [[bid], [ask]] shape (see the L2 Order Book page). nLevels is a Dwellir-specific optimisation not available on the public Hyperliquid API.

Understanding nSigFigs

nSigFigs controls price aggregation. Use 5 for full granularity (matching what the native bbo channel returns); lower values aggregate prices and may not reflect the true best level.

We tested l2Book(nLevels=1, nSigFigs=5) against the public bbo channel and confirmed 100% price match across BTC, ETH, and SOL.

Use Cases

Price Feeds & Tickers

Display live mid-price or last price with minimal data overhead.

Spread Monitoring

Track bid-ask spread in real-time for market quality assessment.

Execution Triggers

Fire orders when the best bid or ask crosses a threshold.

Multi-Coin Dashboards

Subscribe to BBO for many coins simultaneously with low bandwidth (1 level per coin vs 20).

Latency-Sensitive Strategies

Smaller payloads = faster parsing. BBO messages are ~10x smaller than full 20-level book updates.

Subscription Management

Switching Between BBO and Full Depth

# Subscribe to BBO
await websocket.send(json.dumps({
    "method": "subscribe",
    "subscription": {"type": "bbo", "coin": "BTC"}
}))

# Later, switch to full depth (20 levels)
await websocket.send(json.dumps({
    "method": "unsubscribe",
    "subscription": {"type": "bbo", "coin": "BTC"}
}))

await websocket.send(json.dumps({
    "method": "subscribe",
    "subscription": {"type": "l2Book", "coin": "BTC", "nSigFigs": 5, "nLevels": 20}
}))

Get Access

Ready to integrate real-time Hyperliquid BBO data?

• Volume Calculator - Estimate monthly message volume
• Contact Sales - Get your WebSocket credentials
• Dashboard - Manage your subscription

Stream institutional-grade Hyperliquid order book data with Dwellir's ultra-low latency infrastructure.