Hyperliquid Open Interest Guide 2026: How to Read OI, Caps and the API

The short version: open interest (OI) is the total size of perp positions that are still open on a market. On Hyperliquid the API reports it in coins (openInterest in metaAndAssetCtxs), so you multiply by the mark price to get dollars. OI on its own says nothing about direction; you read it together with price, funding and volume. When a market hits its open interest cap, orders that would increase OI are rejected, but you can always reduce or close. The list of capped perps is one API call away: perpsAtOpenInterestCap.

What open interest means on Hyperliquid

Every perp trade has a buyer and a seller. When a new long meets a new short, open interest goes up. When both sides close, it goes down. When one trader hands an existing position to another (an existing long sells to a new long), OI stays the same. So OI measures how many contracts are outstanding, not how much "bullish" or "bearish" money is in the market: for every open long there is an equally sized open short.

Two details matter when you pull the number yourself:

• Units: the openInterest field is in units of the asset (BTC, ETH, HYPE…), not USD. Dollar OI = openInterest × markPx.
• Scope: each perp DEX is reported separately. A plain metaAndAssetCtxs request returns the first (main) perp DEX; builder-deployed HIP-3 markets need the dex parameter. If you add up "total Hyperliquid OI", say which DEXes you included.

A real snapshot: the biggest markets by open interest

We pulled the main perp DEX from the public API on 17 October 2026 at 07:05 UTC and converted OI to dollars with the mark price at that moment:

Perp	Open interest (coins)	Open interest (USD)	OI / 24h volume
BTC	41,150	≈ $3.36B	1.24
ETH	1,075,086	≈ $2.62B	2.88
HYPE	19,870,528	≈ $1.59B	5.73
SOL	5,426,827	≈ $0.57B	1.95
ZEC	465,656	≈ $0.54B	2.18

Summed across every market on the main DEX, OI was about $11.3B at that moment. These are point-in-time numbers; they change with every fill and every mark price update, so treat them as an example of how to read the data, not as current figures.

The last column is a useful quick ratio. A low OI/volume ratio (BTC at 1.24) means a lot of intraday turnover relative to positions held. A high one (HYPE at 5.73) means positions are being held rather than flipped, so a fast move can hit more held leverage at once.

How to read OI together with price

The classic way to use open interest is to compare its change with the price change over the same window. These are heuristics, not rules, but they explain most moves:

Price	Open interest	Usual reading
Up	Up	New positions are opening and buyers are the aggressive side: fresh longs are driving the move.
Up	Down	Positions are closing into the rally, usually shorts covering. The move can fade once covering ends.
Down	Up	New shorts are pressing the market, or longs are averaging down. Either way, more leverage is being added.
Down	Down	Longs are closing or getting liquidated. A sharp drop in OI with a big candle often marks a flush.

Two extra signals make the reading sharper:

• Funding. Rising OI with increasingly positive funding means longs are crowding and paying shorts every hour; rising OI with negative funding means the opposite. The API rate is hourly: in our snapshot BTC showed 0.00125% per hour, the baseline rate, while HYPE was slightly negative. Our funding rate guide shows how that turns into real PnL.
• Liquidations. A sudden OI drop during a fast move is usually forced closing. If you hold leverage in that market, check your distance to liquidation with our liquidation guide; in extreme cases auto-deleveraging (ADL) also closes positions and shows up as an OI drop.

Open interest caps: why your order gets rejected

Hyperliquid limits how large open interest can get on some markets, typically smaller or riskier listings. When a perp is at its cap, the exchange stops anything that would add exposure. The order statuses in the API make the rules explicit:

• positionIncreaseAtOpenInterestCapRejected: the order would increase your position while OI is capped.
• positionFlipAtOpenInterestCapRejected: the order would flip you from long to short (or the other way), which also adds OI.
• tooAggressiveAtOpenInterestCapRejected: the order price is more aggressive than the oracle price while the market is at its cap.
• openInterestCapCanceled: a resting order was canceled because it became too aggressive while OI was at the cap.
• openInterestIncreaseRejected: the order would increase open interest too quickly.

What you can still do at the cap: reduce and close. Reduce-only orders, take-profits and stop-losses that shrink your position are not adding OI. If you trade capped markets, prefer reduce-only exits and keep your TP/SL setup sized to the position so it never tries to flip you.

To see which perps are capped right now, ask the API:

curl -s -X POST https://api.hyperliquid.xyz/info \
  -H "Content-Type: application/json" \
  -d '{"type":"perpsAtOpenInterestCap"}'

When we ran it for the snapshot above it returned ["CANTO","FTM","JELLY","LOOM","RLB","VINE","ZEREBRO"]: small markets, none of the majors. Pass "dex":"<name>" to check a builder-deployed DEX instead.

Caps on HIP-3 (builder-deployed) markets

Builder-deployed perps, such as the stock and commodity markets covered in our TradFi perps guide, have two kinds of caps according to the Hyperliquid docs:

• Notional caps (absolute position size × mark price), enforced both on the whole DEX and per asset. The deployer can set a custom cap per asset, but it must be at least the larger of 1,000,000 units of the collateral asset or half of the current open interest.
• Size caps (absolute position size), enforced per asset and currently a constant 1B per asset.

In practice, a HIP-3 market can be capped even when the main DEX market for a similar asset is not, so check the right dex before blaming your margin.

Pull Hyperliquid open interest with Python

No keys or wallet are needed; this is all public read-only data. The script below ranks the main DEX by dollar OI, adds hourly funding and the OI/volume ratio, and prints the capped list:

import requests

API = "https://api.hyperliquid.xyz/info"

def post(body):
    return requests.post(API, json=body, timeout=10).json()

meta, ctxs = post({"type": "metaAndAssetCtxs"})
rows = []
for asset, ctx in zip(meta["universe"], ctxs):
    oi_coins = float(ctx["openInterest"])
    mark = float(ctx["markPx"])
    rows.append((asset["name"], oi_coins, oi_coins * mark,
                 float(ctx["funding"]), float(ctx["dayNtlVlm"])))

rows.sort(key=lambda r: r[2], reverse=True)
for name, coins, usd, funding, vol in rows[:10]:
    print(f"{name:8} OI {coins:>16,.2f} coins  ${usd/1e6:>9,.1f}M  "
          f"funding/h {funding*100:+.4f}%  OI/24h vol {usd/vol if vol else 0:.2f}")

print("At OI cap:", post({"type": "perpsAtOpenInterestCap"}))

The universe list and the asset contexts come back in the same order, which is why zip works. To track OI over time, run it on a schedule and store the rows; the API gives you the current value, so history is something you build. For more endpoints, see our Hyperliquid API Python guide.

Common mistakes when using open interest

• Comparing coins to dollars. 41,150 BTC and 19.9M HYPE are not comparable until you multiply by mark price.
• Reading OI as direction. High OI means lots of positions, not lots of longs. Use funding and price action to infer who is crowded.
• Ignoring the DEX. Main DEX and HIP-3 DEXes have separate OI and separate caps.
• Using mid instead of mark. Hyperliquid margins, liquidates and computes unrealized PnL with mark price (see mark vs oracle price), so use mark for dollar OI too.

Follow OI and your own positions in one place

Market-wide OI is context; what pays the bills is how your own positions react to it. Hyperfolio's Markets hub shows mark price, funding and open interest per market (for example BTC), and the free app at app.hyperfolio.fun tracks your Hyperliquid positions, real PnL including fees and funding, and Smart Money wallets. It is read-only: you paste an address, no keys and no signatures. If you are opening a new Hyperliquid account, the referral code HYPERFOLIO gives you 4% off trading fees (details in our referral code guide).

FAQ

Is Hyperliquid open interest shown in USD or in coins?

The API returns it in coins (the openInterest field). Interfaces that show dollars multiply it by the mark price.

Does rising open interest mean the price will go up?

No. Rising OI only means more positions are open. Combined with a rising price it suggests new longs are driving the move; combined with a falling price it suggests new shorts. Funding helps confirm which side is crowded.

Why can't I open a position on a Hyperliquid market?

If the order status says something like positionIncreaseAtOpenInterestCapRejected, the market is at its open interest cap. You can still reduce or close, but you can't add exposure until OI falls below the cap. Check the list with perpsAtOpenInterestCap.

Does the main OI figure include HIP-3 markets?

No. Each perp DEX is reported separately; use the dex parameter on metaAndAssetCtxs and perpsAtOpenInterestCap to query a builder-deployed DEX.

Do I need an API key to read open interest?

No. The info endpoint is public. Keys and agent wallets are only needed to place orders.

Where can I see historical open interest?

The info endpoint returns the current value. For history you either store snapshots yourself (the script above on a schedule) or use a data dashboard that already records them.