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A backtest takes one wallet’s actual trade history and replays it through your copy-trade configuration, then tells you what that configuration would have done.
A backtest never places an order and never moves funds. It reads a tape and does arithmetic. Nothing you do in the backtester touches your Polymarket account.
The backtester lives in the web terminal.

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What you configure

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The run

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The strategy

The strategy half of the form is the deployable subset of a copy trade: sizing, sides, reverse copy, the price and value bands, the per-trade bounds, the spend caps and the market gates. The field names and the accepted ranges are identical to the live form, on purpose: a configuration that backtests must be one you can save as a copy trade without editing it. Each is documented in Copy trade settings. That is a promise about the form, not about the outcome. The same numbers do not always behave the same live — slippage inverts, decisions are made per fill rather than per swept order, and spend caps revolve in the simulator but not live. See Backtest fidelity before you deploy one. Four controls are simulation-only and have no copy-trade equivalent. The form badges them, and a result names the ones the run actually engaged:
  • Starting capital
  • Category allowlist
  • Required keywords and excluded keywords (matched against the market)

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Slippage means something different here

In a live copy trade, slippage is a tolerance: how far the book may have moved and still fill you. In the backtester it is a cost: the fill is booked at a worse price, and it always happens. Because of that, the backtester defaults to 1%, not the live default of 30. A run left at 30 would charge a 30% haircut on every single fill — on one measured wallet, that one substitution accounted for around 85% of the gap between a reported −788kandthe+788k and the +2.09M the same tape produces at a realistic cost. An explicit 0 is a real setting and is honoured: fills are priced at the leader’s own price. It does not mean “unset”.
Deploying a backtested configuration as a live copy trade deliberately does not carry the slippage over. Carrying a 1% simulated cost across as a 1% live tolerance would silently turn a validated configuration into one that rejects most of the fills it was validated on. The deploy leaves both fields blank and the live default of 30 stands.

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What the backtester refuses

Take-profit, stop-loss and balance-level TP/SL cannot be submitted. All six arm against a continuous price path between fills, and a tape only has prices at the leader’s own fills. They are rejected, not ignored. A request carrying sl_percentage comes back as an error rather than a result that reads “your stop-loss strategy made money” for a simulation that never had a stop-loss. The same guard catches a misspelled field name, which would otherwise run the whole simulation at the wrong size.

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The queue

Runs are queued, not executed inline.
1

Queued

You may hold two pending-or-running backtests at a time. Submitting a third is refused with a message saying so — the only thing that clears it is one of your own runs finishing.
2

Fetching the leader's trade tape

The slow part. A full tape is pulled page by page from an upstream with an account-wide rate limit that live copy trading also spends. This is why a run takes minutes and why a page view will never start one for you.
3

Loading market metadata and resolutions

Every market the leader touched has to be priced and, where it resolved, settled.
4

Simulating your configuration against the tape

Your filters, sizing and caps, fill by fill.
The run page shows the stage and a progress percentage while it works, and you can leave and come back — the run is not tied to your browser.
Submitting a configuration identical to one already queued or running reopens that run instead of starting a second: it is the same deterministic answer bought twice with heavy upstream quota.A finished run is never handed back in its place. The tape genuinely changes underneath a fixed window — old fills gain detail later, markets in the window resolve after it, and a run may have been cut short by its fetch budget. Re-running is the honest default.

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Afterwards

A finished run keeps its result, the exact configuration that produced it, and the window it covered. From there you can:
  • Read it — see Reading a result for what the reliability banner is telling you.
  • Trust it appropriately — every result ships with a standing list of the ways the simulation is not reality. See Backtest fidelity.
  • Deploy it as a copy trade. The deployable half of the configuration is carried across, the simulation-only controls are dropped, and the copy trade is created paused so nothing mirrors until you switch it on.
A backtest also harvests the leader’s tape as a side effect, which is what fills in the taker share and execution profile on their trader profile.

Backtest fidelity

Every way a simulated fill differs from a real one.

Reading a result

Reliability, boundary exposure, data gaps and fee confidence.

Copy trade settings

The strategy half of the form, field by field.

The backtester

Using it in the terminal.