If you have it on your phone, it will do
No need to print as long as you have it on your phone.
They can find your reservation based on an approved I D. You may have to wait in a moderately slow line though. As has been mentioned, your best bet is to have the App. Second best is to use the kiosk. You can still print things ahead of time if that is your style.
You can download the app for whatever airline your using on your phone. You can then check in on your phone, ticket can also be sent to your phone by barcode. You will also receive any flight or gate changes on the phone as well.
you can also use an app for the appropriate airline. if you are checking in luggage the kiosks will dispense those to put on your luggage for turn-in.
I think you can just come to terminal and take boarding pass from kiosk. It's quick these days as crowd is less.
Check in at home and print your boarding pass if you can. The lines at the airport are a mess
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