92Score
Nautilus Tradernautechsystems/nautilus_traderA Rust-powered, Python-driven platform where the backtest code and the live code are the same.
★ 31k stars · Advanced · updated 2026-10
Backtesting
Best Python Backtesting Engines on GitHub | Test It Before It Costs You
Engines that test a strategy on history with fees and slippage, before real money is involved.
In plain English
A backtester replays your strategy on years of old prices, with fees and slippage, so you find out it loses money before you do.
What Should You Know Before Picking a Backtesting Repo?
Every strategy looks brilliant in your head. A backtest is the cold shower. It answers the only question that matters: would this have made money after fees, slippage and bad fills?
These engines range from friendly to industrial. 
Backtrader is the classic that taught a generation of Python traders, though it has not been updated since 2024. Nautilus Trader runs the same code for testing and live trading, which removes a nasty class of surprises. 
QuantConnect LEAN powers a whole commercial platform.
One warning. A backtest that looks too good usually is. If you tune a strategy until history looks perfect, you have built something that predicts the past. Test on a period you did not tune on.
Who this lane is for
- Anyone who wants proof before putting money behind an idea
- Python users ready to write strategy rules as code
- Traders moving from TradingView scripts to something more serious
Where to start: Backtrader has the most tutorials for beginners. If you plan to go live later, Nautilus Trader or LEAN save you a rewrite.
Backtesting, Explained in One Picture
Every Backtesting Repo We Verified, Ranked by Community Score
- 92ScoreNautilus Tradernautechsystems/nautilus_trader
87ScoreQuantConnect LEANQuantConnect/LeanThe open-source engine behind QuantConnect. Institutional-grade backtesting in C# or Python.
★ 22k stars · Advanced · updated 2026-10
84Score
vectorbtpolakowo/vectorbtVectorized backtesting that tests thousands of parameter combinations in seconds.
★ 9.6k stars · Intermediate · updated 2026-10
80Score
PyBrokeredtechre/pybrokerA Python backtester built for machine learning strategies, with walk-forward analysis baked in.
★ 3.7k stars · Intermediate · updated 2026-10
63ScoreBacktradermementum/backtraderThe classic Python event-driven backtester. Huge community, no updates since 2024.
★ 24k stars · Intermediate · updated 2024-08
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Backtesting Repos FAQ
What is the best backtesting library in Python?
It depends on the job. Backtrader is easiest to learn, vectorbt is fastest for testing many settings, and Nautilus Trader or QuantConnect LEAN are built for strategies you plan to run live.
Is Backtrader still maintained?
Its last code update was in August 2024. It still works and has a huge community, but new broker changes will not be fixed by the original author.
Why do backtests fail in live trading?
Common reasons are ignoring fees and slippage, peeking at future data by accident, and over-tuning settings until they fit history. Paper trading after the backtest catches most of these.