Perpetual futures

Three cards in four in this catalogue list perpetuals in their coverage, which makes it the most common derivative here and the one the coverage field says least about. The word names a contract shape. Which contract — which venue, which margin currency, which index — is what a reader needs and the flag does not carry.

How it works

A dated future converges on spot because at expiry it settles against the underlying. A perpetual has no expiry, so nothing forces that convergence; the funding rate is the substitute. When the contract trades above its index, longs pay shorts, and the payment pulls the price back. OKX's own guide puts it in one sentence: perpetual futures "do not have an expiration date", and the funding mechanism exists "to ensure the futures' prices and index prices converge periodically". Converge periodically, not stay equal — the gap between a perpetual and spot is the basis, and it is real.

Every perpetual therefore has at least three prices attached to it: the last trade on its own book, the index it is pulled toward (a weighted spot price from other exchanges), and a mark price the venue computes from both to value positions. Margin is posted against the position, and when it runs short the venue closes it — a liquidation, which is the second cash flow a perpetual has that spot does not.

Linear and inverse are two different contracts. A linear perpetual is sized in the coin and settled in the quote currency: OKX's USDT-margined BTC contract is 0.01 BTC and settles in USDT. An inverse one is sized in dollars and margined and settled in the coin: OKX's crypto-margined contract is 100 US dollars and settles in BTC, so its profit and loss in BTC is not a straight line in the dollar price. Hyperliquid documents its contracts as linear perpetuals with the oracle price in USDT and the collateral in USDC — a third combination.

The names are not standard either. CCXT's market structure types it swap, "for perpetual swap futures that don't have a delivery date", and puts the settlement currency after a colon: BTC/USDT:USDT is a linear perpetual funded in USDT and BTC/USDT:BTC an inverse one funded in BTC. Bybit's market endpoints take a category of spot, linear or inverse, and the word "perpetual" appears nowhere in the parameter. Kaiko's instrument class is perpetual-future.

In the United States a perpetual is a five-year future. Coinbase Derivatives certified its nano Bitcoin Perp Style Futures with the CFTC on 26 June 2025 as a five-year, cash-settled contract, the first expiring on the third Friday of December 2030, with only one contract listed for any five-year period. Funding is calculated every hour by the clearing house and settled through its mid-day and end-of-day margin runs. It behaves like a perpetual and is legally a dated future, which is why a vendor's "perpetuals" filter may or may not contain it.

Why it matters here

A perpetual's price is not the spot price. A chart or a price API built from perpetual trades carries the basis in it, and during a squeeze the basis is the move. Check which market a series came from before comparing it with anything. The ticker will not tell you: on Binance BTCUSDT names both the spot pair and the USDⓈ-M perpetual, and on Bybit's kline endpoint omitting category returns linear by default — the perpetual, not spot. Where the Bitcoin price comes from is the longer version of why two "BTC prices" disagree.

One venue's perpetual is not another's. Funding interval, contract size, margin currency and the index constituents are all set per venue, and sometimes per symbol. An aggregate that sums perpetuals across exchanges has converted at least some of them, which is the problem open interest runs into at full size. A card that says it covers perpetuals should also say which venues and whether it keeps linear and inverse apart. The venues' own APIs — Binance, Bybit, OKX — answer these questions for one book at a time. CCXT answers them in one naming scheme across many.

Decentralised perpetuals are the same contract on a different stack. Hyperliquid, dYdX and Aster list perpetuals with the same funding-and-index mechanics, but the data arrives through the venue's own API, indexer or Binance-shaped endpoints rather than through the aggregators most cards were built around. See the Hyperliquid SDK, the dYdX v4 clients and Aster's API. Aster also shows the shape stretching past crypto: more than a hundred of its perpetuals are tagged as stocks, and they keep trading after the underlying has closed. What a tokenized stock is covers what that weekend price is.

A perpetual treated as spot is a different instrument. A backtest that loads perpetual candles and charges neither funding nor liquidation has deleted both cash flows the position has. What a crypto backtest silently assumes goes through which engines charge them. For the data itself, the how-tos on funding and open interest and on watching liquidations take the two perpetual-only series one at a time.