Data Reconciliation: How FollowCheck Checks Its Polymarket Trade Data
A backtest is only as good as its trade data. FollowCheck indexes trades directly from Polygon and checks them against an independent source every day.
Daily reconciliation
- Every day we sample 100 trades and compare them, one by one, with Polymarket’s public trades API: market, outcome, side, price and size.
- The latest result — how many were checked and how many matched — is on the status page.
- Long-run match rate since launch: TBD.
- Our fillsOrderFilled events indexed from Polygon
- Daily sample100 trades picked every day
- Field by fieldMarket, outcome, side, price and size vs. the Polymarket Data API
- PublishedChecked and matched counts on the status page
What can differ
- Timing: very recent trades may not be indexed yet. The status page shows how far the index lags the chain head.
- Representation: one match on-chain can emit several fill events. We store each maker fill once, so volume isn’t double counted.
Verify any trade yourself
Every trade on a wallet page has Details → Verify on-chain, which opens the transaction (or its block) on Polygonscan. We keep block numbers and log indexes for every fill, so every trade the site uses can be traced back to the chain; simulated results are computed from those trades.
Related: methodology