What is that blue mark at the play marker?

[PosadaPhotography]

Lately I've been seeing a blue line at the point of the play marker:

What is that and what does it indicate?

[R Neil Haugen]

If you are way zoomed into the timeline, that would be the bar showing the currently selected frame.

Why?

The playhead is not "in-between" or separating frames ... ever.

The playhead of any NLE is always attached to the next frame. Which confuses many users at first.

[PosadaPhotography]

Thanks...I just never remember seeing it before.

[R Neil Haugen]

Naturally! As most of the time,  none of us are "zoomed in" that much, to actually see it shown.

[Ann Bens · Accepted solution]

It represents 1 frame. It has always been present.

When you zoom out of the timeline the marker gets too small to see and disappears.