Citizens of Australia, Andorra, Austria, Brunei, Belgium, Bulgaria, Canada, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hong Kong, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malaysia, Malta, Monaco, The Netherlands, New Zealand, Norway, Poland, Portugal, Romania, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, United Kingdom, United States of America and the Vatican State can get a free-of-charge entry visa upon arrival at Abu Dhabi International Airport.
GCC citizens do not need a visa to enter the UAE.
Citizens of all other countries will need to apply for a Tourist, Transit or Visit Visa prior to their trip. If you are flying with Etihad Airways, a visit visa may be arranged for you upon request. If you have booked your trip through a travel agency, in most cases they will be able to arrange this for you.
Five, four and three star hotels can apply for visas on behalf of guests who have booked a stay with them. Please note that not all five, four and three star hotels have this system in place. Make sure you check with your preferred hotel if they offer this service. This service does not currently apply to guests staying in hotel apartments
While the airline, travel agency and hotel can apply for your visa, please make sure you give yourself enough time for it to be approved, and note that they do not take responsibility if the visa is declined.
Otherwise, you will need to apply for a visa through your nearest UAE embassy. An eye scan will be required at the airport.
Source: Visit Abu Dhabi