Bar replay hides everything after a bar you choose and reveals it forward one bar at a time. You see the chart as it looked at that moment, with no knowledge of what came next.
It is the closest thing to trading a past session honestly, because the information you are missing is genuinely missing rather than merely off screen.
Start a replay
Right-click the bar you want to start from and choose to begin replay there. On a touch screen, long-press does the same thing.
Everything after that bar disappears until you reveal it.
The controls
Space plays and pauses.
Step moves forward one bar at a time.
Rewind moves back. Hold either to repeat, or use Shift to jump ten bars at once.
Speed controls how fast playback runs.
The scrubber lets you move through the replay directly rather than stepping.
No lookahead
This is the part that makes replay worth using. The chart genuinely does not have the later bars while you are stepping through, so you cannot accidentally read ahead, and indicators calculate only from what has been revealed.
An indicator during replay shows what it would have shown at the time, not what it shows today with the benefit of the full series.
Live data keeps running
While you are replaying, live bars continue arriving in the background and are buffered. When you leave replay the chart catches up rather than showing you a gap, so you do not lose your place in the real session.