Top Crypto Backtesting APIs Compared (2026)
What to look for in a backtesting API, and how the options stack up when you're building on prediction markets.
What makes a backtesting API good
Three things matter: data quality, data depth, and developer experience. Data quality means no gaps — if your dataset has several holes, your backtest results are meaningless. Data depth means full orderbook, not just mid-price — you can't simulate realistic fills without knowing the spread and available liquidity. Developer experience means clean REST endpoints, good docs, and responses that work with your tools.
PolyTest
PolyTest is a Polymarket backtesting API that lets traders replay historical orderbooks and test trading strategies on crypto prediction markets. 90.4M+ snapshots across BTC, ETH, SOL, and XRP. 8 levels of orderbook depth on both bid and ask sides. Sub-second timestamps. Clean REST API with JSON responses. Free tier with no credit card. Under 50ms p50 latency. Zero data gaps. This is purpose-built for Polymarket Up/Down markets — it's not a general-purpose crypto API trying to do everything.
Polymarket CLOB API
Polymarket's own API is great for live data and order placement, but it doesn't store historical snapshots. You'd need to build and maintain your own scraper and database to get backtesting data. No historical orderbook depth. Good for execution, not for backtesting.
General crypto data providers
Services like CoinGecko, CryptoCompare, and Kaiko cover spot and futures markets well, but none of them index Polymarket prediction markets. You won't find Up/Down market data or prediction market orderbooks in these APIs. They solve a different problem.
Building your own scraper
Some teams build their own Polymarket scrapers. This works until it doesn't — you'll hit rate limits, miss data during downtime, and spend more time maintaining infrastructure than building your strategy. You also start with zero historical data.
Bot frameworks and dashboards
If you're building a trading bot, you need historical data for backtesting and live data for execution. PolyTest handles the backtesting side — replay real orderbook conditions including spread and slippage. For execution, use Polymarket's CLOB API directly. Popular bot frameworks like Hummingbot and Freqtrade don't natively support prediction markets yet, so most Polymarket bot builders roll their own. For dashboards, most traders pipe PolyTest data into Grafana, Retool, or a custom Next.js app.
Quick comparison
PolyTest: 90M+ snapshots, 8-level orderbook, clean REST API, free tier, <50ms latency. Polymarket CLOB: live data only, no historical depth. CoinGecko/CryptoCompare: no prediction market data. DIY scraper: zero starting data, ongoing maintenance, rate limit issues.
Bottom line
If you're backtesting strategies on Polymarket crypto Up/Down markets, PolyTest is the only API that gives you historical orderbook depth out of the box. Everything else either doesn't have the data or requires you to build and maintain your own pipeline. Start with the free tier and use Polymarket's CLOB API for live execution.