microM8’s web-debugger provides a number of handy debugging functions including a variety of break-points, stepping, memory editing, recording and rewind inside an easy-to-use web-based interface.

You can start the debugger by pressing Control-Shift-B once you boot an Apple II disk. The debugger starts paused.

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The debugger is designed to provide a constant view of the CPU state, program counter, recently executed instructions and memory lookahead. A tabbed section on the right-hand side provides panes for video representation, memory, softswitches, breakpoints and general settings. Along the top are a number of buttons related to CPU execution and speed, and recording and playback functionality.Using the recorder allows for easy revisiting of errors. You can travel back to just before the incident and then either trace or step-through execution to pinpoint exactly what went wrong. This is much easier than having to run a trace from scratch and hoping that the incident reoccurs (which as we know it often does not.) 
A number of controls are provided for playback. These allow for playback at various speeds in both reverse and forward, and in one second and 100ms intervals. Using the controls you can travel back to precisely before the incident, saving time.