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Price Candles

GET /v1/markets/{condition_id}/candles
Returns OHLCV candlesticks. The price ticks come from Polymarket’s CLOB /prices-history endpoint — those arrive as {t, p} (single price per tick, not OHLC), so PolySimulator buckets them server-side into the requested interval and aggregates open (first tick), high (max), low (min), close (last tick) per bucket. Volume is sourced from your internal fills on PolySimulator, not Polymarket’s chain volume.
Before the May 8, 2026 launch, this endpoint returned O = H = L = C for every tick (no bucketing). Bots using technical indicators on the prior output saw flat candles. The current implementation produces proper OHLC variation when the underlying tick stream has it.

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Query Parameters

ParameterTypeDefaultDescription
outcomestringfirst available outcomeOutcome label (e.g. Yes, No, Up, Down)
intervalstring1hBucket interval — see table below

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Available Intervals

IntervalBucket size
1h1 hour (default)
6h6 hours
1d1 day
1w1 week
maxTreated as 1d for bucketing — gives the longest meaningful intra-day signal
Only 1h, 6h, 1d, 1w, and max are supported. Sub-hour intervals (1m, 5m, 15m) and any other unrecognised value return HTTP 400 with {"error": "INVALID_INTERVAL", "message": "...", "supported_intervals": ["1h", "6h", "1d", "1w", "max"]}. There is no silent fall-back to 1h — the request fails loudly so you don’t render an empty or mis-bucketed chart.Sub-hour granularity is unavailable because the upstream Polymarket CLOB /prices-history feed is hourly-granular — we can’t reconstruct 5-minute buckets from 1-hour samples. (Polymarket’s own /prices-history enum does include 1m and all, which PolySimulator does not support.)

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Example

curl -H "X-API-Key: $API_KEY" \
  "https://api.polysimulator.com/v1/markets/0x0f49db97f71c68b1e42a6d16e3de93d85dbf7d4148e3f018eb79e88554be9f75/candles?outcome=Yes&interval=1d"

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Response

[
  {
    "t": 1777939200,
    "o": "0.2615",
    "h": "0.2680",
    "l": "0.2595",
    "c": "0.2625",
    "v": "98.0000"
  },
  {
    "t": 1778025600,
    "o": "0.2605",
    "h": "0.2605",
    "l": "0.2475",
    "c": "0.2475",
    "v": "3.0000"
  }
]
FieldTypeDescription
tintegerUnix-second timestamp of the start of the bucket. For 1h every value is a multiple of 3600.
ostringOpen — first tick price in the bucket
hstringHigh — max tick price
lstringLow — min tick price
cstringClose — last tick price
vstringVolume — sum of share-quantity from your internal FILLED orders within the bucket. "0" when no internal fills. Polymarket’s chain volume is not included.
The v field reflects your own simulated trade flow only. To measure Polymarket-wide volume on a market, query the underlying tokens via the Polymarket Gamma API directly. PolySimulator’s volume is meant for “did my own backtest fill?” sanity, not for liquidity proxies.
If a bucket has only a single tick, o == h == l == c — that’s correct behaviour for a slow-moving market, not a bug.

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Backtesting Example

import requests
from decimal import Decimal

BASE = "https://api.polysimulator.com"
headers = {"X-API-Key": "YOUR_API_KEY"}

# Fetch hourly candles for the past day. Pass outcome explicitly when
# you want a specific side; default is the first outcome.
candles = requests.get(
    f"{BASE}/v1/markets/0x0f49.../candles",
    headers=headers,
    params={"interval": "1h", "outcome": "Yes"},
).json()

# Simple moving average crossover (close prices)
prices = [Decimal(c["c"]) for c in candles]
if len(prices) >= 48:
    sma_short = sum(prices[-12:]) / 12   # last 12 hours
    sma_long  = sum(prices[-48:]) / 48   # last 48 hours
    if sma_short > sma_long:
        print("Bullish crossover — consider BUY")
    else:
        print("Bearish crossover — consider SELL")

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Migrating from Polymarket

Polymarket’s CLOB /prices-history returns the raw {t, p} tick stream without bucketing. If you’re porting a bot that does its own bucketing client-side, you can either:
  1. Trust ours — drop your bucketing code and use the t/o/h/l/c/v shape directly. The interval parameter behaves identically to a pandas resample("1H").agg({"o": "first", "h": "max", ...}).
  2. Keep yours — fetch raw ticks via Polymarket’s Gamma API, since PolySimulator does not (yet) expose the un-bucketed feed. Cross-host strategies that compare the two should bucket identically client-side.

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Next Steps