For years the first price an index trader saw after Friday was the futures reopen on Sunday evening. Index perps now trade through the whole weekend. By Sunday night there are two markets pricing the same Monday open. They are built differently, and the differences tell you how to weigh each one.
What each one is
S&P 500 futures are exchange-listed contracts with an expiry date. They are cleared centrally and used by institutions hedging real portfolios. They stop on Friday evening and resume on Sunday evening. Globex and the overnight session covers how that tape behaves once it is running.
The S&P 500 perp is a perpetual contract on Hyperliquid. It has no expiry, settles in a stablecoin and holds no shares. Funding keeps it near its reference price. It never pauses. Stock perps, explained has the mechanics.
What the perp has
Hours. From Friday evening to Sunday evening the perp is the only one of the two with a price. If news lands on Saturday morning, the perp shows a reaction on Saturday morning. Futures show theirs later, all at once, as an opening gap of their own.
The perp also gives you a path. You can see whether a move happened in one step or built over a day, and whether it held. A futures gap on Sunday evening is a single jump with no history behind it.
What futures have
Depth and participants. The futures market is far larger, and its users include many of the funds that will trade the cash open. On 4 October 2026 the S&P 500 perp held about $349 million of open interest. That is real weight for a weekend market and small beside index futures. A price formed in a deeper market takes more money to move, so it is harder for one order to distort.
How the two fit on Sunday night
Before futures reopen, the perp is the only read. Treat it as a market price on another venue. Once futures reopen there are two reads. When they agree on direction and rough size, a second and deeper crowd has arrived at the same place. When they differ, the gap between them is information, and when the perps and the futures disagree works through it.
Neither one is the open. The cash open is set on Monday morning by its own auction, with orders that neither market has seen. Both reads can be right on Sunday night and both can be somewhere else by the bell.
Where the dealer map comes in
Both markets tell you where price is. Neither tells you what that level means for SPY or QQQ options. That comes from dealer positioning: the gamma flip, the walls and the expected move. A perp has none of those and neither does a future. Read the level from the perp or the futures tape, then read its meaning from the map, the way the dealer map after an overnight gap describes.
Trader shows the index perps’ move since the cash close on its Perps & Futures tab, next to dealer positioning for SPY, QQQ and IWM.