How do I change my Apple ID password, or reset it if I forgot it and I'm locked out?

Know it and just changing it: on iPhone go to Settings > tap your name at the top > Sign-In & Security > Change Password (it asks for your device passcode first). Locked out: on any Apple device use 'Forgot password' on that same screen, or go to iforgot.apple.com, Apple verifies you with your trusted device passcode or a trusted phone number and lets you set a new one. What makes reset painless is having a trusted phone number and recovery contact set up in advance. Turn on two-factor authentication too, it's the biggest protection for an Apple ID.

The device passcode is basically the master key now, on a trusted iPhone you can reset the Apple ID password using just the passcode, no old password needed. That's why keeping your passcode private matters so much.

Set a recovery contact and trusted phone number BEFORE you're locked out (Settings > your name > Sign-In & Security). Without them, Apple account recovery can take days; with them it's minutes.