What is the difference between backtesting and paper trading?

Backtesting asks what would have happened under historical assumptions. Paper trading asks how the strategy behaves now, with today's market conditions, operational quirks, and real-time decision loop.

What to remember

Rejecting obviously weak ideas early
Comparing variants under the same assumptions
Studying turnover, exposures, and path shape before you touch live capital
Forward-only evidence instead of hindsight

They answer different questions

A backtest is a historical simulation. It is the fastest way to check whether an idea ever looked coherent across past data.

Paper trading is a live rehearsal. It shows whether the same logic still behaves the way the backtest implied once time starts moving forward again.

What backtests are good for

Backtests are great at narrowing a research space. They are bad at proving that your execution, data cleanliness, or current edge will hold in the next market regime.

Rejecting obviously weak ideas early
Comparing variants under the same assumptions
Studying turnover, exposures, and path shape before you touch live capital

What paper trading adds

Paper trading does not replace a backtest. It tells you whether the clean historical story survives contact with real time.

Forward-only evidence instead of hindsight
A reality check on slippage, timing, and operational discipline
A way to compare the current market to the historical baseline you thought you understood

Why Alphora treats both as part of one loop

The useful workflow is not backtest or paper trade. It is compose, verify, paper trade, and compare. That is why Alphora's public docs, catalogue pages, and examples all point back to the same strategy lifecycle.

Next in Research workflow

Why does out-of-sample matter more than a clean in-sample backtest?