How to fix Photo's freezing when uploading photos to Walgreens App?

Can you give us more information? Like, what do you mean by "upload photos for example to Walgreens photo app?" Freezing up isn't good at all, but I don't use Walgreens, so it's hard to know what's going on. Are you using Safari to access the Wallgreens web site? If so, are you using the "media selector" to go through Photos (while on Safari) and choose your pictures?

If that's what you're doing, then one trick to try is to, outside of Safari, export your selected pictures from Photos to a folder on your Desktop, using the menu File>Export>Export nn Photos. Then point Walgreens to that folder.

But I'm concerned about the freezing. Even if the above works, try these things to see if it clears up:

• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes. Safe Mode is different for different computers, so see this: 

Start up your Mac in safe mode - Apple Support 

• Make a new user and see if the same problem recurs with it
• Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens. You can create a new Library by closing Photos and then option-clicking on the Photos icon.

The idea is to find out if the problem is with the Library, with your account, or with caches and login items, and stuff like that. One of these steps may fix the problem, but their failure to work also helps figure out what's happening.

Let us know how it goes....

Are you using the Walgreens Photo app which is primarily for creating passport photos locally? Or are you using a browser to upload to Walgreens photo site and order prints?

I've ordered prints from Walgreens online site but I export the photo to the Desktop and upload via Safari from there.