In this guide
Every transaction on PolyGram and Polymarket is processed via a Central Limit Order Book — the identical order-matching system employed by NASDAQ, NYSE, and virtually all major financial exchanges worldwide. Grasping how CLOB operates will sharpen your approach as a prediction market participant. This guide walks you through the essentials.
What Is a Central Limit Order Book?
A Central Limit Order Book (CLOB) is a digital ledger containing all active buy and sell orders for a given asset, organised by price level and chronological sequence. Upon arrival of a fresh order, the matching engine seeks to pair it with opposing orders already present in the book.
Within prediction markets, the "asset" refers to a YES or NO share tied to a particular event. The CLOB for "Will Bitcoin exceed $100K in 2026?" displays every outstanding order seeking to acquire YES shares alongside every outstanding order seeking to dispose of YES shares (or equivalently, to acquire NO shares).
Reading the Order Book
- Bids (buy orders): Participants offering to purchase YES shares at a stated price or lower. Arranged from highest to lowest price.
- Asks (sell orders): Participants offering to sell YES shares at a stated price or higher. Arranged from lowest to highest price.
- Best bid: The uppermost price at which a buyer is presently prepared to acquire YES shares
- Best ask: The lowermost price at which a seller is presently prepared to dispose of YES shares
- Spread: The gap separating best ask from best bid. Narrow spread indicates robust market depth.
How Orders Match
Upon submission of a market order (acquiring at prevailing rates), the CLOB matching engine:
- Identifies the current best ask (minimum seller price)
- If your bid price ≥ best ask: transaction settles at the ask price
- Your order receives complete or partial fulfilment according to accessible supply
- Unexecuted portions persist in the book as a fresh bid
Limit orders function in the same manner but trigger only when market conditions align with your predetermined price threshold.
Why CLOB Matters for Traders
- Price improvement: Your order settles at the most competitive available rate, avoiding artificial premiums
- Transparency: All pending orders remain visible, enabling informed trading judgement
- No counterparty risk: The CLOB matching system, rather than an intermediary, manages your transaction
- Better prices vs AMM: CLOB-structured markets typically deliver narrower spreads relative to automated market makers (AMMs)
CLOB vs AMM in Prediction Markets
Polymarket's CLOB (employed by PolyGram) differs fundamentally from AMM-structured prediction markets such as earlier iterations of Augur. CLOBs deliver granular pricing and order-book depth; AMMs furnish perpetual liquidity availability yet incur wider slippage on substantial orders. For the majority of prediction market scenarios, CLOB architecture proves advantageous.
FAQ
- What is slippage in a CLOB prediction market?
- Slippage materialises when your order volume surpasses the liquidity accessible at the optimal price point, forcing portions of your order to settle at less favourable rates. PolyGram calculates and displays projected slippage prior to order confirmation.
- Can I place limit orders on PolyGram?
- Absolutely — you may designate a ceiling price for YES share acquisition or a floor price for NO share acquisition. Your order sits within the CLOB awaiting market movement to your specified level or cancellation by you.
- How often does the CLOB update?
- The Polymarket CLOB refreshes instantaneously without interruption. PolyGram synchronises with these modifications through its CLOB connection, with negligible processing delay.