What a split carousel actually is

A split carousel is one picture cut into vertical panels and posted as a single carousel post. As the reader swipes, the panels line up and the whole thing reads as one continuous image scrolling sideways. It works because carousel slides sit edge to edge in the viewer, so a cut that lands in the right place disappears.

That is a different job from a grid mural, which is one image cut into square tiles and posted as separate posts so the profile grid assembles into a picture. If that is what you are after, the Instagram grid maker does that one, and the posting order for it is counter-intuitive enough that it needs its own page.

Getting the cuts right

Two things decide whether a split carousel works.

Pick the slide shape before you pick the picture. A 4:5 slide is much taller than it is wide, so four of them side by side need a source image roughly three times wider than it is tall. If your source is not that wide, the tool crops from the centre to make it fit, and you lose the left and right edges. Starting from a genuinely wide image is the difference between a panorama and a centre crop.

Keep anything important away from the seams. A face or a word that lands on a cut is split across two swipes and reads as a mistake rather than an effect. Use the preview strip above, pull the slides apart, and check what each one contains on its own — every slide has to survive being looked at individually, because plenty of people will only see the first one.

What you get

A ZIP containing one PNG per slide, named slide-01.png upwards in swipe order. Upload them in that order and the panorama reads left to right. All of them are the same pixel size, none of them are watermarked, and no part of the process touches a server.