Because the perpetual trades under the index
Funding is negative when the perpetual is trading below its spot oracle price, and the holders of short positions then pay the holders of longs rather than being paid by them. The sign comes from the premium index, which measures the gap between what the order book will actually fill and the oracle price.
That is all the sign carries. A negative rate is the price of holding a side for an hour, not an opinion about where the price is going.
How far under the index it takes
The documented 8-hour rate is F = P + clamp(interest rate - P, -0.0005, 0.0005), with the interest term fixed at 0.01% every 8 hours. Put those figures in and the clamp does something worth knowing: while the premium index sits between -0.04% and +0.06%, it absorbs the whole gap and the rate is exactly the interest term, positive.
So funding does not flip at the first sign of a discount. By the same arithmetic, the 8-hour rate turns negative only once the average premium index falls below -0.05%, and it is then the premium plus 0.05%. One eighth of that is exchanged each hour. A negative rate on a screen is therefore already a real discount, not noise around zero.
The premium itself is measured against the depth of the book, not its top: the gap between the oracle price and the impact prices, the average execution prices to trade impact_notional_usd on each side, 20000 USDC for BTC and ETH and 6000 USDC elsewhere. It is sampled every 5 seconds and averaged over the hour.
An example
Say the average premium index over an hour is -0.2%. The clamp is pinned at its ceiling of +0.05%, so the 8-hour rate is -0.15% and the hourly rate one eighth of that, -0.01875%. The payment is position_size * oracle_price * funding_rate, so a short of 10,000 dollars pays 1.88 dollars an hour to the longs, about 45 dollars over a day if the rate held. It rarely holds.
What a negative rate says, and what it does not
It says what it measures and no more: over that hour, trading 20000 or 6000 USDC into the book landed below the oracle price on average.
- It does not say how many shorts there are. Open interest counts contracts still open, and every contract is one long and one short. No public figure names a crowded side.
- It does not say the discount will last. The premium is resampled every 5 seconds and the rate recomputed every hour, from that hour alone.
- It is not free money. A long being paid still carries the whole price risk of the position, which can be many times an hour of funding in a single move.
- It is not a signal. It is a cost that has changed sign for both sides, published after the hour it describes.
Receiving funding does not reduce a position's risk. Funding on Hyperliquid is capped at 4% an hour, while a liquidation can take the entire margin of a position in one move: in isolated margin the isolated margin and the position go, and in cross margin a backstop liquidation transfers the cross positions and the cross margin together. The rate changes what a position costs to hold, never what it can lose.
Where to see it
The funding page of this site lists the markets whose funding was negative at the snapshot next to the highest positive ones, as Hyperliquid's public API gave them. When no market is negative at that moment the page says so rather than showing an empty table, which happens more often than the question suggests.
Each market page is the plainer view: the average hourly funding over seven days and the share of those hours in which longs paid shorts. A snapshot can catch one odd hour; seven days show whether a market really pays its shorts. In the position cost calculator a funding received is shown and is not counted as a gain.