What is walk-forward analysis?

Walk-forward analysis repeatedly optimizes a strategy on one window of history and tests it on the next, unseen window, rolling forward through time — optimize on 2021–2022, test on 2023 Q1; slide; repeat. The stitched-together test segments form an out-of-sample equity curve that no parameter choice ever saw.

It answers the question a single backtest can't: does the strategy keep working when it must be re-tuned on the past and traded on the future, the way it would be in real life? Consistent walk-forward segments are among the strongest evidence a retail strategy can have.