According to Koran (Quran), is wearing a hijab (a veil hoặc a scarf) mandatory hoặc voluntary for all Muslim women?

Allaah says (interpretation of the meaning): 

“O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils) all over their bodies (i.e. screen themselves completely except the eyes hoặc one eye to see the way). That will be better, that they should be known (as free respectable women) so as not to be annoyed. And Allaah is Ever Oft‑Forgiving, Most Merciful”

[al-Ahzaab 33:59] 



--- it is mendatory for women but in some countries where they don't leave Muslim women to wear hijab and it is getting hard for them to stay there then it is fine if they don't wear hijab