Order Book

Access L2 order book depth from Polymarket’s CLOB for any market.

Order Book

GET /v1/markets/{condition_id}/book

Returns the CLOB L2 order book snapshot for a market’s primary token.

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Request

curl -H "X-API-Key: $API_KEY" \
  "https://api.polysimulator.com/v1/markets/0x1a2b3c/book?outcome=Yes&depth=5"

Parameter	Type	Default	Description
outcome	string	—	Filter by outcome label (e.g. Yes, No)
depth	int	10	Number of price levels per side (max 50)

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Response

{
  "token_id": "71321...",
  "bids": [
    {"price": "0.64", "size": "500.0"},
    {"price": "0.63", "size": "1200.0"},
    {"price": "0.62", "size": "3000.0"}
  ],
  "asks": [
    {"price": "0.66", "size": "400.0"},
    {"price": "0.67", "size": "800.0"},
    {"price": "0.68", "size": "2500.0"}
  ],
  "mid": "0.65",
  "spread": "0.02",
  "timestamp": "2026-02-06T12:00:45Z"
}

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Understanding the Book

Field	Description
bids	Buy orders sorted by price (highest first)
asks	Sell orders sorted by price (lowest first)
mid	Average of best bid and best ask
spread	Difference between best ask and best bid
price	Price level
size	Total shares available at that price

Liquidity Assessment

from decimal import Decimal

book = api.get_order_book("0x1a2b3c...")

# Calculate total bid liquidity
bid_liquidity = sum(
    Decimal(level["size"]) for level in book["bids"]
)

# Calculate total ask liquidity
ask_liquidity = sum(
    Decimal(level["size"]) for level in book["asks"]
)

spread = Decimal(book["spread"])

print(f"Spread: {spread}")
print(f"Bid depth: {bid_liquidity} shares")
print(f"Ask depth: {ask_liquidity} shares")

Check the book before large orders. If your order size exceeds the top-of-book liquidity, you’ll walk through multiple price levels and experience slippage. Use slippage protection to guard against this.

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Next Steps

• Markets — Browse available markets
• Placing Orders — Trade with real book depth