“Is Invisalign painful?”

I definitely would not use the word 'painful'. I will just say that with each aligner change (which is typically weekly), your teeth will feel mild pressure to the extent that they may be tender for 2-3 days, and then subsides. When you feel this mild pressure and tenderness, you will know that they are working to straighten your teeth and give you the result you're wanting. So, it's no pain...just mild pressure! Patients LOVE it...especially when they see the steady progress!!!

I would describe the sensation for as annoying, until you get used to wearing your trays and having your teeth move during treatment. I have never had a patient complain of pain during Invisalign therapy.

You will be realigning your teeth to a better fit.  This change can cause soreness.  I have personally done traditional braces, twice! To me uncomfortable when I was actively moving teeth.  Softer food diet for a time.  Well worth it, and I am a foodie!!  Love my food   Do Invisalign with a trained orthodontist, for the best results.

Not completely "painless". You can get some soreness when you change to a new tray.