Polymarket CLOB API: Order Book, Prices & Orders (V2, 2026)

API · Reference

The CLOB (Central Limit Order Book) at clob.polymarket.com is where orders rest and match. You read the book, prices and tick size with no auth, and trade (place / cancel orders, read your balance) with API credentials and signing. This is the CLOB V2 reference: collateral is pUSD, fees are on-chain, and makers pay zero.

Read the order book (no auth)

from py_clob_client_v2 import ClobClient   # pip install py-clob-client-v2
client = ClobClient(host="https://clob.polymarket.com", chain_id=137)   # read-only: no key
book = client.get_order_book(token_id)
mid  = client.get_midpoint(token_id)
print(book.bids[0].price, book.asks[0].price, mid)

// polymarket_client_sdk_v2 (official, repo rs-clob-client-v2)
use polymarket_client_sdk_v2::clob::{Client, Config};
use polymarket_client_sdk_v2::clob::types::request::OrderBookSummaryRequest;
let client = Client::new("https://clob.polymarket.com", Config::default())?;
let book = client.order_book(&OrderBookSummaryRequest::builder().token_id(token_id).build()).await?;

curl -s "https://clob.polymarket.com/book?token_id=$TOKEN_ID"

Sample response

{
  "market": "0x...",
  "bids": [ { "price": "0.62", "size": "1400" }, { "price": "0.61", "size": "900" } ],
  "asks": [ { "price": "0.64", "size": "1100" }, { "price": "0.65", "size": "2000" } ]
}

Read endpoints

Limits are high: CLOB ~9,000 requests / 10s, /book and /price 1,500 / 10s, and over-limit requests are throttled, not rejected. More on 429s.

Place & cancel an order (auth)

One call builds, signs (the V2 order struct) and posts your order. You choose an order type:

from py_clob_client_v2 import (ClobClient, OrderArgs, OrderType,
                               PartialCreateOrderOptions, Side, OrderPayload)

# authenticated client (creds from create_or_derive_api_key - see Authentication)
client = ClobClient(host="https://clob.polymarket.com", chain_id=137, key=PK, creds=creds)

resp = client.create_and_post_order(
    order_args=OrderArgs(token_id=token_id, price=0.62, side=Side.BUY, size=10),
    options=PartialCreateOrderOptions(tick_size="0.01", neg_risk=False),  # read both off the market
    order_type=OrderType.GTC,            # GTC, GTD, FOK or FAK
)
# resp -> {"success": true, "orderID": "0x...", "status": "live"}
client.cancel_order(OrderPayload(orderID=resp["orderID"]))   # cancel

Fees: only takers pay, and the rate curves

Makers are never charged. Takers pay a fee that is not flat - it scales with the market's uncertainty and varies by category. The formula:

fee = shares × feeRate × p × (1 - p)      # p = share price, 0..1

The p·(1-p) term means the fee peaks at 50/50 and shrinks toward the 1¢ and 99¢ edges - so a near-certain outcome is cheap to take, a coin-flip is dear. Per-category taker feeRate:

Read the live rate per token with GET /fee-rate-bps?token_id= rather than hardcoding it; fees round to 5 decimals (min 0.00001 pUSD). Makers paying zero is why most edge-free bots quote rather than take.

Negative-risk (multi-outcome) markets

Multi-candidate events ("who wins the election?") are neg-risk markets: their outcomes are linked, so a No share in one outcome converts into a Yes share in every other through the Neg Risk Adapter - capital-efficient, but mechanically different. They run on different contracts from binary markets, so you must pass neg_risk=True in the order options (read the market's negRisk flag off Gamma). Omit it and the order is signed against the wrong exchange and rejected.

Conditional tokens: split, merge, redeem (beyond the book)

Underneath every market is the Conditional Token Framework (CTF). Outcome tokens are ERC-1155 tokens, and every Yes/No pair is backed by exactly $1.00 of pUSD locked in the CTF contract. That gives you three primitives the order book alone does not:

Split and merge are the basis of CTF arbitrage: if Yes + No trade below $1.00 on the book, buy both and merge back to $1.00; if they trade above $1.00, split $1 into a fresh pair and sell both. Redemption settles through the ConditionalTokens contract once the oracle posts the outcome on-chain - a position shows redeemable: true on the Data API when it is claimable. Position IDs derive via getConditionId → getCollectionId → getPositionId.

Advanced: RFQ & combo markets (for serious makers)

Beyond the order book, Polymarket runs a Request-for-Quote (RFQ) system, used especially for combo markets - existing markets bundled into multi-leg composite positions. The flow has three phases: a taker requests a quote, makers compete with quotes, and the chosen maker gets a last look to confirm or decline before execution.

• Discover combos: GET /v1/rfq/combo-markets (public; limit 1-100, cursor, exclude). Each combo exposes two position IDs (Yes = index 0, No = index 1).
• Quote as a maker: POST combos-rfq-api.polymarket.com/v1/maker/quotes (L2 auth). You generate the quote_id yourself, and send rfq_id, maker_address, signature_type, a signed Exchange order, and price_e6 / size_e6 as six-decimal fixed-point strings (the *_e6 convention avoids float precision loss).
• Last look: while the RFQ is AWAITING_MAKER_CONFIRMATION, respond CONFIRM, DECLINE, or let it TIMED_OUT.

RFQ state machine: CREATED → COLLECTING_QUOTES → AWAITING_REQUESTER_ACCEPTANCE → AWAITING_MAKER_CONFIRMATION → EXECUTING → FILLED (else FAILED / EXPIRED / CANCELED / REJECTED). Subscribe to the RFQ WebSocket gateway for live state. This is niche - most bots only need the CLOB book above - but it is how multi-leg and combo liquidity gets priced.

Check balance & allowance

client.get_balance_allowance(...)   # collateral (pUSD) and conditional-token allowances

If this shows zero allowance, approve pUSD/CTF to the V2 exchange contracts before ordering.

Next: Authentication & wallets · WebSocket: stream the book · Fix a CLOB error.