How to Build a Polymarket Trading Bot (2026)

Polymarket runs around the clock, and automated traders already account for a large share of its order flow. If you are placing orders by hand, you are competing against bots that never sleep. The good news: building your own Polymarket trading bot no longer means standing up servers and gluing together half-documented APIs. This guide walks through it end to end with Banger.

What you need

• Python 3.11 or newer.
• A Banger account (free) for paper trading.
• A Polymarket account and key when you are ready to go live. You keep your own keys; Banger never custodies funds.

1. Install Banger

Install the SDK and CLI in one package:

pip install bangertrades

2. Write a strategy

A Banger strategy is a small Python class. This one fades markets that have drifted to an extreme implied probability inside the final 24 hours, on the theory that extreme-probability markets often underprice late jump-to-resolution risk. It is quarter-Kelly sized so a string of true outcomes does not blow up the book.

from decimal import Decimal
from banger import Strategy, signals
from banger.risk import RiskEnvelope
from banger.venues.polymarket import Polymarket


class FadeOverconfidence(Strategy):
    name = "fade_overconfidence"
    venues = [Polymarket()]
    universe = signals.polymarket_markets(
        time_to_resolution_lt="24h", min_volume_usd=25_000
    )
    risk = RiskEnvelope(
        max_position_usd=Decimal("50"), max_daily_loss_usd=Decimal("250")
    )

    async def on_market_tick(self, market, tick, ctx):
        yes = float(tick.yes_price or 0)
        if yes >= 0.97 and ctx.can_open_position():
            await ctx.place(self.venues[0], market, side="no",
                            size=ctx.kelly(edge=yes - 0.5))

3. Paper-trade against the live book

Before risking a cent, run the strategy in paper mode. It executes against live Polymarket data with simulated fills, so you can watch orders, fills, logs, and P&L on the dashboard and confirm the logic does what you expect.

banger run fade_overconfidence.py --paper

4. Go live with hard limits

When the paper results convince you, add your Polymarket credentials, keep the risk envelope (per-trade cap, daily loss stop, max open positions, kill switch), and promote the same code to live. The risk caps are enforced on every order, so a bug cannot quietly run your book to zero.

A note on legality

US persons trade Polymarket event contracts legally through Polymarket US, a CFTC-regulated exchange. Automated and API trading is permitted. Always check the current terms for your jurisdiction before going live.

That is the whole loop

Write or clone a strategy, paper-trade it, then promote the same code to live with hard limits. You can run many small strategies under one risk envelope rather than betting everything on one idea. Start free and paper-trade your first Polymarket strategy today.