Polymarket Open Interest, Explained

Forecast markets report price and volume; open interest is not part of the documented data feed. The nearest official proxies are depth (current resting size) and, on-chain, token balances (outstanding shares per address).

Neither equals futures OI: depth is limit orders that can be cancelled, and on-chain balances include tokens held by non-trading wallets. Both still carry signal.

• Depth sum across the ladder: total resting contracts on both sides, per token, over time.
• Top-of-book ratio (bid vs ask size) is the lightweight proxy most models use.
• Outstanding token supply from chain explorers or Dune tables: actual shares issued, updated on settle.
• Volume-to-depth ratios to separate recycling trades from genuine holdings.

For intrabar questions — is interest accumulating into a resolution — depth sums at 250ms are the practical metric, and the archive records them continuously.

For structural questions — how much capital is parked in a market — the on-chain token supply is the real number, at the cost of being attribute-aligned only when positions move.

The honest conclusion: OI on Polymarket is a construct. Recorded depth is the live-proxy dataset; chain tables are the audit trail. Use both and label the measurement.

• Sample the frame-level open interest for one market across a day and compute the daily change; OI is the slow variable and the trend, not the level, is the signal.
• Compare OI to daily volume: the ratio is the days-of-turnover-in-OI number that describes how long the exposure lives.
• Correlate the OI path with the one-sided share around a reprice; a collapse in OI during a reprice is the honest sign of participants exiting.
• Check the OI series against the ticker for the same instant; the archive OI is a series and the ticker is a point — record both.

Open interest is the count of outstanding market positions — the exposure that has not closed — and on Polymarket it is captured per frame so the series tracks the market's lifetime instead of a snapshot.

The measured venue story is the pairing with volume: with median trades of 42,254 shares against thin tops, OI is often a modest reservoir of position being redistributed on every reprice, and the OI-to-volume ratio captures that busy-ness.

The OI habit that pays: sample the frame-level open interest daily, compute the daily change, and hold it next to daily volume. The ratio tells you turnover in days, and watching it double around a collapse describes the exit pressure without any guesswork.

Open interest on this venue is best read as a companion to volume rather than alone: OI change measures position building and exit, volume measures turnover, and the ratio estimates how many days of turnover sit in open positions. Publishing the two side by side for a reprice window shows exactly what the reprice rearranged.

Open interest is the venue's position reservoir, measured per frame and trended across the market's life.

Pair OI with volume to read exposure turnover; OI alone is a level, the ratio is the behavior.

Watch OI's collapse around reprises and settlements; the series records exactly when participants exit.

Open interest is the slow variable of the venue; this page pairs with the metrics and ticker pages for where the series lives.

Its OI-to-volume ratio is cited by the liquidity and market-making pages as the exposure-turnover lens.

Watching OI collapse around reprises and settlements is the behavioral habit this page establishes.

Open interest is the position reservoir, tracked per frame against volume turnover.

Watch its collapse around reprises and settlements; the series records exactly when participants exit.

• Order book data
• Price history
• Crypto data
• Provider matrix