// GLOSSARY

EIP-712

An Ethereum standard for signing typed, structured data instead of opaque byte blobs. Polymarket CLOB orders are EIP-712 messages: the fields you sign (token, price, size, expiration) are exactly the terms that can settle onchain.

EIP-712 defines how to hash and sign structured data — named fields with types — so that a signature commits to specific, human-inspectable terms rather than an unreadable hex string. Wallets can display what's being signed, and contracts can verify it cheaply.

Why Polymarket uses it

A Polymarket order is not a row in a private database; it's an EIP-712 message your Polygon key signs, specifying the outcome token, side, price, size, and expiration. The operator matches these messages off-chain, and settlement contracts verify the signatures onchain. The practical consequence: a match can only settle on terms you actually signed.

What it means for your integration

Placing orders programmatically means producing valid EIP-712 signatures — in practice you use Polymarket's official client libraries rather than hand-rolling the hashing, and the signing key must live somewhere safe (see API key signing). Kalshi involves no wallet signatures at all, which is one of the deeper API differences between the venues — compared in Kalshi API vs Polymarket API.