Hotels are required to upgrade if, at the time of check-in, there is availability of a higher category room or suite for the entire duration of the guest’s stay.

There is no guarantee of an upgrade at any time before actually checking-in in person at the hotel on the arrival date. Of course, no hotel does room assignment on a first-come basis. Because usually room assignment is done daily the evening prior to, or early in the morning of, the arrival day, it is common for the upgrade to show up in advance on the app. But even this is not guaranteed—that suite can still be sold until and up to the elite guest’s actual check-in.

Some hotels will do the courtesy of pre-blocking the upgraded room if the guest requests by email or through the app, or even unprompted. But those instances are rare.