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

EndpointReturns
GET /book?token_id=Full order book (bids / asks).
GET /price?token_id=&side=Best bid or ask.
GET /midpoint?token_id=Mid = (best bid + best ask) / 2.
GET /spread?token_id=Best ask − best bid.
GET /tick-size?token_id=Minimum price increment (round your price to it).

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:

TypeBehaviour
GTCGood-Till-Cancelled — rests on the book until filled or cancelled.
GTDGood-Till-Date — rests until an expiry timestamp.
FOKFill-Or-Kill — fill the whole order immediately or cancel it.
FAKFill-And-Kill — fill what it can immediately, cancel the rest.
 
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"),
    order_type=OrderType.GTC,            # GTC, GTD or FOK
)
client.cancel_order(OrderPayload(orderID=resp["orderID"]))   # cancel
V2 order facts. The signed struct dropped nonce, feeRateBps, taker and expiration and added timestamp, metadata and builder; the Exchange EIP-712 domain version is "2". Fees are collected on-chain at match — makers pay 0, only takers pay. Before trading you must approve pUSD + conditional tokens to the three V2 contracts (see the allowance fix).

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.

Yes / No token IDs. Each binary market has two token IDs. Don't hardcode which is Yes — read the parsed outcomes array (Gamma returns it, and clobTokenIds, as JSON-encoded strings you must decode) and map by name.

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

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