Ethereum Polymarket mispricing — share vs spot, every second.
When Ethereum moves, Polymarket ETHshare prices don't move with it tick-for-tick. They move with the Chainlink oracle that resolves the market — and that oracle lags by seconds, sometimes longer. The gap between the live exchange price and the lagged oracle is exactly what our crypto bundle exposes, refreshed every second.
ETH spot crosses $2,300 on Coinbase. Chainlink still reads $2,278. The 'ETH ≥ $2,300 by close' market hasn't repriced because nothing on-chain has triggered an update yet.
Two endpoints. The full mispricing picture.
/v1/crypto/oracle-lag/ETH/v1/crypto/spread/ETH# Live ETH oracle lag curl -H "X-API-Key: $DPM_KEY" \ "https://api.datapolymarket.com/v1/crypto/oracle-lag/ETH?minutes=5" # In Claude Code (via MCP) > "Find Polymarket ETH markets where Chainlink lags Binance by >0.4%"
Why the ETHoracle lags (and why that's the trade)
Polymarket ETH markets resolve on the Chainlink ETH/USD aggregator. Same deviation+heartbeat behaviour as BTC, with slightly larger deviation thresholds.
The aggregator updates when one of two things happens: enough oracle nodes report a new price that crosses the deviation threshold, or the heartbeat fires (every hour or so). Between updates, the on-chain price is by definition stale. Polymarket markets that resolve on this aggregator therefore price a slow-moving truth — even though the real-world ETH price is moving every millisecond.
For a casual punter that's just trivia. For a Polymarket trader it's a structural mispricing. If the Chainlink number is going to update upward in the next 30 seconds and a YES share at the threshold is trading like the old number, the expected value flips before the oracle does. That window — from when the underlying crosses the threshold to when the oracle reports it — is the trade.
We don't guess at the trade. We give you both numbers, side by side, every second, with the gap precomputed. Whether you market-make against it or just take the obvious shares is up to you.
ETH mispricing data, free for 3 days.
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