$ man -k hyperliquid # section 7: conventions and behaviour · field-tested, dated, numbered

Handbook: field notes for Hyperliquid builders

Short notes on API behaviour that the documentation leaves vague, written from running collectors, paper traders and a liquidation radar against the public API around the clock. Each note says what we observed, when, and how we changed our code. Corrections welcome.

• data-semantics-open-interest-and-l2book(7)openInterest is the sum of both sides, l2Book shows 20 levels per side, most large resting orders sit outside them, delisted assets stay in meta, and other field semantics we had to learn by measuring.2026-09-30
• hip3-fees-growth-mode-funding(7)The taker-fee formula for HIP-3 markets, where to read growth mode and the deployer fee scale from the API, and a three-month replay showing funding at roughly thirty times the fee bill.2026-09-30
• hyperliquid-rate-limits-in-practice(7)Per-IP limits, which /info calls are heavy, what a 429 storm looks like from the inside, and the pacing rules that stopped us punching holes in our own data.2026-09-30
• websocket-15-user-cap(7)Address-based WebSocket subscriptions on Hyperliquid stop at 15 distinct users per IP. The API tells you once, on the error channel, and keeps the socket open. Here is how we found it and what we do instead.2026-09-30