Tick replay is a property that can be optionally enabled on NinjaScript indicators and strategies which will ensure that the market data (bid/ask/last) that went into building a bar is loaded in the exact sequence of market data events. This guarantees that your indicators and strategies are historically calculated tick-per-tick exactly as they would have been if the indicator/strategy was running live during a period. Tick replay can be enabled for indicators used in Charts, Market Analyzers, and Strategies.