How to build a trading bot for Polymarket (2026 guide)

A trading bot is just software that places and manages orders faster and more consistently than you could by hand. On Polymarket, most bots fall into four archetypes:

• Market making: quote both sides of a market to earn the spread, plus a share of the platform's liquidity rewards.
• Cross-market / cross-venue arbitrage: capture price gaps between correlated markets, or between Polymarket and another venue such as Kalshi.
• Event-driven / news reaction: react to a result or headline faster than the book reprices.
• Inventory / hedging: manage and offset exposure you have taken on elsewhere.

All four sit on the same foundation: programmatic access to the order book. If the terms “bid”, “ask”, “maker” and “taker” are new, read markets explained first, then come back.

Before a single line of code runs, you need the account and access set up:

• A funded account. On the international platform that means a wallet funded with USDC on Polygon; on Polymarket US it means a verified, funded US account. Our registration guide covers both.
• CLOB API access and allowances. You generate API credentials and set the on-chain token allowances that let the exchange contract move your USDC when orders fill.
• Order signing. Every order is cryptographically signed by your wallet before it is posted, so the bot needs secure access to the signing key (typically via a dedicated wallet, not your main one).

Polymarket exposes trading through its CLOB API, with official clients: py-clob-client for Python and clob-client for TypeScript. You do not need to hand-roll HTTP calls; the clients wrap authentication, order construction and submission.

The order lifecycle is straightforward once you see it end to end:

1. Read the book: pull current bids and asks for the market's token id.
2. Build an order: outcome token, side, price and size.
3. Sign it: your wallet signs the order (Polymarket uses a proxy-wallet model, so the signing wallet authorises trades against your funded balance).
4. Post it: submit as a resting limit order (maker) or one that fills immediately (taker).
5. Handle fills: listen for fills, update your inventory, and requote or hedge.

The maker/taker choice is the crux of bot economics: makers generally pay no fee and can earn rewards, while takers pay a fee for immediacy. A market-making bot lives almost entirely on the maker side.

The simplest useful bot quotes both sides around the mid-price, then adjusts as it accumulates inventory. The sketch below is illustrative pseudo-code to show the shape of the loop. Real bots add error handling, rate-limit backoff, partial-fill logic and the risk controls further down this page.

# Illustrative market-making loop (pseudo-code, not production-ready)
from py_clob_client.client import ClobClient

client = ClobClient(host, key=API_KEY, ...)   # authenticated client
MARKET        = "0x..."   # token id for the Yes outcome
HALF_SPREAD   = 0.02      # how far off mid we quote each side
SIZE          = 50        # shares per side
MAX_INVENTORY = 500       # hard position cap

while running:                       # your main loop
    book = client.get_order_book(MARKET)
    mid  = (book.best_bid + book.best_ask) / 2
    inv  = get_position(MARKET)       # your own inventory tracker

    # skew quotes against inventory so you don't pile up one side
    skew = (inv / MAX_INVENTORY) * HALF_SPREAD
    bid  = round(mid - HALF_SPREAD - skew, 2)
    ask  = round(mid + HALF_SPREAD - skew, 2)

    cancel_all(client, MARKET)
    if inv <  MAX_INVENTORY:
        client.post_order(build_signed_order(MARKET, "BUY",  bid, SIZE))
    if inv > -MAX_INVENTORY:
        client.post_order(build_signed_order(MARKET, "SELL", ask, SIZE))

    sleep(REQUOTE_SECONDS)            # requote on a timer or on fills

The important idea is the inventory skew: as you accumulate Yes shares, you quote a little lower on both sides to encourage selling back down, so you earn the spread without drifting into a large directional position you never intended.

A bot that only runs while your laptop is open is a liability. A minimal reliable setup:

• Hosting: a small always-on server such as an AWS EC2 instance, close to the API for low latency.
• Process management: a supervisor (systemd, pm2 or similar) that restarts the bot if it crashes.
• Monitoring and alerts: push key events and errors to a channel you actually watch, for example a Telegram bot, so you know within seconds if something breaks.
• Logging: record every order, fill and cancel so you can reconstruct what happened and measure performance.
• Secrets handling: keep API keys and the signing key out of your code, in environment variables or a secrets manager, never committed to a repo.

The fastest way to lose money with a bot is to let a bug run unattended. Hard, non-negotiable limits matter more than clever strategy:

• Max position per market and overall, enforced before every order.
• Inventory caps that stop the bot quoting the side that would breach them.
• Max drawdown: a daily or total loss limit that halts trading when hit.
• Circuit breaker / kill switch: an automatic stop on abnormal conditions (stale data, wild spreads, repeated errors) and a manual one you can trigger instantly.

Treat these as the parts you build first and test hardest. A strategy that is merely mediocre survives; a strategy with no kill switch does not.

For a market-making bot, returns come from two places: the spread you earn when both your quotes get filled, and the liquidity rewards Polymarket pays makers for posting competitive two-sided orders, distributed daily around midnight UTC.

Here is the honest part. Those rewards are real, but they exist to compensate for adverse selection: informed traders pick you off when the price is about to move, and naive strategies often bleed exactly what they earn in spread back to those traders. There is no durable edge you can assume, only edge you can measure. Before you scale size, read how to find and measure edge, which covers markout analysis and sizing so you can tell a real advantage from a mirage.