When visiting mosques, female travellers should wear clothing that covers from ankle to elbow, as well as covering decolletage. It's also important to cover your hair with a scarf. Don't worry if it's not expertly wrapped – a few stray strands hanging out from beneath the scarf won't bother anyone.
Does Morocco require head coverings?
Unlike some of the yet more conservative Muslim countries of the Middle East, foreign women being required to cover their head is uncommon according to the Morocco dress code.