Using Duo outside the United States


This article covers using Duo multifactor authentication from locations outside the United States.


Considerations for each Duo factor

Duo mobile app

Push notifications to the Duo mobile app will work in any location as long as your phone has an internet connection. Passcodes can be generated from within the Duo app, no internet connection required.

Phone call and SMS

Successful phone calls from Duo to a mobile phone depend largely on the carrier's international capability, the features enabled for the plan, the phone number's original locale and it's current location. A USA phone number may not be able to receive phone calls in other countries and vice versa if the plan does not include international service, or it is incapable of receiving service in the region. Telephone service in international locales may be less reliable, especially outside North America and Europe, which can affect the ability to receive Duo authentication calls. International mobile phone standards may also lack compatibility with US mobile phones. However, if you have a mobile or landline phone number capable of receiving service in the country you're travelling in, and that phone number is enrolled in your Duo account, the likelihood is greater that you can use the number to complete authentication.

Many of the same factors apply to SMS or text messages while travelling internationally. In many cases, international SMS service is a separate feature from international calling and you should confirm with your carrier that your plan has the appropriate service.

Hardware Token

Hardware tokens do not require an internet connection to operate and can generates codes from any location regardless of country.



The Duo mobile app and hardware tokens are preferred authentication methods to use when travelling internationally. Neither require an internet or phone connection to operate and can function when Wi-Fi or cellular service are unavailable.

If you obtain an international phone number and wish to use it for Duo when travelling, it is important to ensure the number is enrolled with your Duo account prior to your travel. For a step by step guide for enrolling a mobile number on your Duo account, please visit

USA phone numbers can work outside the United States but success may vary depending on your phone, your carrier, your plan and International roaming options.

If planning for a future trip, or in an area where you have SMS capability, you can send 8 backup codes to your phone and print or save those to use at a later time. To obtain the codes, visit an authenticated U of I website such as and when prompted for MFA, click "Enter a Passcode" (you may have to dismiss your default authentication), then at the bottom click "Text me new codes" which will send 8 backup codes to your phone. You can print or save those to use at any time in the future. Each code may only be used once. 


Common Duo issues when travelling internationally

I am not receiving phone calls from Duo when attempting to complete authentication

Check to ensure your phone can receive calls from US phone numbers and that you can dial US phone numbers.

If you have the Duo mobile app enrolled on your account, try connecting to the internet and using a push notification to login. Alternately, you can use a passcode generated from within the app by opening the Duo app and tapping the University of Idaho account that is displayed on the screen.

If you have a mobile phone number from another country, but have not added it to your Duo account, you will not receive Duo calls to that number. Please ensure that it is enrolled with your Duo account by visiting and reviewing your list of devices.

I do not have internet or cell service. Can I still login to my account?

Yes, you can still complete authentication if you have a hardware token or the Duo mobile app enrolled on your account. With the app, you can generate a passcode to enter when logging in by opening the Duo app, tapping the University of Idaho account, and using the 6 digit code that is revealed.