Polymarket Order Types Explained

Polymarket matches limit orders against the resting book. A "market order" or "one-click" in the UI is a limit order priced to trade immediately against the executable side; an "immediate or cancel" also posts and cancels the balance. There is no true market order on the OTC/CLOB.

What this means for the data: every interaction that changes price is an order on the ladder, and the recorded books are the ground truth of how those orders arrived and left.

An incoming limit at a price on or inside the executable side crosses immediately against resting size — first level, then deeper, then (for a one-click) the remainder cancels. An order at a price outside the executable side rests on the ladder, which is why 250ms books show static deep supply at the 0.99 bound.

The measured consequence: executable prices bunch on the 0.99/0.995 grid 98.6% of the time because resting orders sit at the bound, and fills happen by consuming that resting supply.

From the recorded books, order behavior is observable second by second: depth appearing at a level is an order, depth disappearing is a fill or cancel, and the tape (with size and side) shows which happened. This is the raw material for studying queuing, front-running, and bound-sitting.

The honest caveat is the archive's standard one: rows preserve what appeared in the book, not the identity of the trader behind it — order-flow conclusions must stay structural.

The naming layer (limit, one-click, immediates) is interface sugar over one primitive: the limit order. Any strategy that treats Polymarket as if it ran market orders will model fills that never happen; the recorded ladder is the school for the correct habit.

• Makers and takers
• Tick size
• Order book explained