[pbmonster]

Par for the course, really. Still can't zoom into images on Instagram, can you?

The one and only supported image resolution is also lower than any of the screens I use.

The app is really hard to believe from a technical perspective, in general.

[pjc50]

You can pinch-zoom on mobile, but only while you're holding it down. I suspect again this is intentional and the two go together - they don't want you zooming in on limited resolution images, that'll look even worse.

[kevincox]

This is a relatively recent feature. And yes, it is almost certainly because the images are awful quality before zooming in, so they want to limit how obvious this is.