Perpetual Contracts Explained

Concept

A perpetual swap (perpetual contract, “perp”) is a crypto-native derivative designed to track the spot price of an underlying without a fixed delivery date. You are not rolling quarterly contracts; instead, the product stays open until you close it or margin fails. That convenience made perps the dominant retail and professional instrument for leveraged crypto exposure—but the “no expiry” feature is paired with a funding mechanism that keeps the contract tethered to the index over time.

Funding is periodic payment between longs and shorts, set by rules published by the exchange (often proportional to the difference between mark and index, subject to caps and interest components). When perps trade above fair index, longs typically pay shorts; when below, the opposite may hold. You should read XT’s exact formula and schedule in official documentation. Funding is not a “fee” to the exchange in the same sense as commissions; it is peer-to-peer transfer that prices positioning. If you hold through funding timestamps, your wallet balance moves even if price is flat—so carry matters for anyone holding more than a few hours.

No expiry changes how you plan trades. With dated futures, convergence toward spot as expiry nears is part of the story; with perps, basis is managed through funding and arbitrage by sophisticated players. You still care about term structure indirectly: elevated funding can mean crowded longs, and negative funding can mean crowded shorts—but sentiment reads are noisy; always pair them with risk limits and liquidity checks.

Mark price versus last traded price is a core safety concept. Last is the most recent trade; in thin or fast markets it can spike on small size. Mark is typically a blend of index and last (or similar methodology) used for unrealized PnL and liquidation logic so that a brief wick does not cascade liquidations. Your liquidation price and margin ratio therefore follow mark, not necessarily the number flashing on the tape you are watching. Misunderstanding this causes the classic complaint: “Price never hit my liquidation on the chart.” The chart may be last; the engine may be mark.

Index price aggregates spot references from multiple venues (methodology varies). It anchors where the perp “should” trade in equilibrium before funding adjusts incentives. When you see mark hugging index during calm periods, the system is doing its job; when they diverge, pay attention to volatility, dislocations, or exchange-specific rules.

Predicted funding values shown before a funding event are typically indicative; realized prints can differ with last-minute order flow. Some formulas include a small interest component that matters when the premium term is tiny—check whether XT publishes separate pieces or a single blended rate. Strongly positive funding can persist in trending markets when long leverage stays crowded; deeply negative funding can persist in brutal bear phases. Arbitrage and risk limits eventually lean on extremes, but regimes can last longer than a patience budget sized for quick mean reversion. Intraday traders who flatten before each funding avoid the transfer; swing traders and hedgers should budget funding like recurring rent, not a rounding error.

Operational detail: if you leg into hedges, partial fills or API lag can leave you briefly directional at the worst moment. Prefer limits sized to visible depth, confirm both sides, and accept small basis drift rather than lifting offers with market orders in thin books. Your runbook for outages—which leg to cut first if connectivity fails—belongs in writing before adrenaline arrives.

Before trading size, internalize: perpetuals are margin products with funding timestamps; your PnL path depends on price, fees, funding, and leverage. Treat official XT contract pages as the source of truth for funding interval, rate caps, and mark methodology.

Observe on XT

Navigate to a USDT-margined (or coin-margined) perpetual on XT. Open the contract information or details drawer and locate: funding interval (for example, every eight hours), current funding rate, and next funding countdown if displayed.

On the same screen, find index price, mark price, and last price (or equivalent labels). Watch them during a volatile minute: notice whether last moves more erratically than mark.

Read XT’s help or glossary entries for funding rate and mark price so you see the exchange’s own definitions, not a third-party summary.

Practice

1. Pick one perpetual contract on XT and note the next three funding times in your local timezone (from the countdown or schedule).
2. At least 15 minutes before and 15 minutes after one funding event, record index, mark, last, and the published funding rate. Compare how your equity would be affected on a hypothetical small long (calculate directionally: pay or receive).
3. Screenshot or write down XT’s formula reference or help link for funding (for your notes only); bookmark it.
4. In order settings or position panel, find where mark-based liquidation or margin ratio is explained; identify which price field the UI uses for liquidation price estimates.

Checkpoint

Q1: What is the main role of the funding mechanism in perpetual contracts?

• A) To replace all trading fees
• B) To periodically align the perpetual’s price with the index by transferring value between longs and shorts
• C) To guarantee that perpetuals always equal spot tick-for-tick
• D) To remove the need for margin

Correct: B. Funding incentivizes convergence and prices carry; it does not eliminate fees or margin.

Q2: Why do exchanges often use mark price rather than last traded price for liquidation checks?

• A) Because last price is always manipulated and mark is always correct
• B) To reduce the impact of short-lived, thin-book spikes on forced closures
• C) Because mark price ignores the index completely
• D) Because liquidation only applies to spot traders

Correct: B. Mark smooths manipulation and discontinuity risk relative to a single last print.

Q3: If you hold a long perpetual through a funding interval where longs pay shorts, what happens all else equal?

• A) Your position size automatically doubles
• B) You typically pay funding from your margin balance to shorts, reducing equity if the rate is positive for payers
• C) The exchange refunds your fees
• D) Your liquidation price moves further away automatically

Correct: B. Funding transfers affect wallet equity; exact sign depends on published rate and your side.