The United States government requires all nonimmigrants to carry a paper copy of their I-94 with them at all times as evidence that they have legally registered to be in the US. Visiting students and scholars need to carry their I-94 form with them at all times while they are in the United States.
If the visitor is completing a check-in with the International Students and Scholars Office (ISSO), the visitor can request a copy of their I-94 form. If the visitor is coming on a business visa and is not required to complete a check-in with ISSO, then the visitor will need to access the I-94 form available online.
The digital I-94 can be saved to a mobile device, but it is also recommended to print a copy to keep in a wallet, purse, etc.
For more information, review the Department of Homeland Security's website for travelers visiting the United States.