Change circle line thickness in Photos app on iPhone

Click the shape to add. (I chose a square in this example)

This will place a “default shape” on the image.

Then …

The tool button on the left end of the “add a shape” toolbar changes the shape’s fill color.

The 2nd button from the left (the red & black “X”) changes the shape’s outline color AND the outline width.

You’re welcome.

FWIW, it’s not addressed in the iOS user guide.

Edit photos and videos on iPhone - Apple Support

I'm guessing that you mean in Markup section in Edit mode in Photos, and you want this?

I used the line width tool to increase the border width.

Is that what you need?

You didn't say what device you are using. My screenshot is from a Mac, so I guess that's not you. Are you asking about an iPad or an iPhone? On my iPad I did the same thing by using "Add Shape" and making a big Red circle and a smaller blue circle, and moving the blue circle into the red on. Here:

I've left it unfinished to show me moving the blue circle in.

I don't think that I know how to do this on an iPhone. I can't even find "Add Shape…"

I can't visualize what you mean? Can you post an example so we can see exactly what you're referring to?

lal312, I think I'm missing something. How are you changing the size of the border?

This shows a rectangle being added to a screenshot; with “no fill” and a 15pt yellow border.

Ahh--good. But I think I'll stick with the Mac....

A Mac is the FAR better way to edit !!!

This “revised” markup tool was introduced maybe 3 iOS versions ago and it drove me nuts while re-learning how to make it work consistently.