I decided to reference Nielson's usability heuristics to evaluate Instagram UI, specifically these five: Visibility of system status, Error Prevention, 
Aesthetic and minimalist design,  Flexibility and Efficiency of Use and  Consistency and standards. 

 

1. Visibility of system status

As you enter Instagram app you can see that it was visibility of the system status as it shows the wireframes of the app so the user can see that the app is loading. 

 

2.  Error Prevention

If you login with the wrong acount is easy to switch. The menu on the left side facilitate the use of the app for people who has more than one acount.

 

3. Aesthetic and minimalist design

Menus,icons, words, and phrases are kept short and simple leading the focous to the content of the user. 

 

4. Flexibility and Efficiency of Use

The Instagram algorithm has a few things that are great in user efficiency for an example it shows images of the other users
based on what the users liked so the prioritty is whats they are interest in seeing.

 

5. Consistency and standards

Instagram apps executes consistency and standards perfectly. Icons, words, navigation, micro-interactions are very
consitent.