How to disable two factory authentication?

For new Apple IDs created with two-factor authentication enabled and for Apple IDs that have had two-factor enabled for more than two weeks, there is no means to disable two-factor authentication. If you just enabled two-factor, it can be disabled within two weeks using the email message received when it was first enabled.

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require higher security.

Please see this Apple Support document for more information: Two-factor authentication for Apple ID - Apple Support

LD150 wrote:

"...If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings. ..."

Maybe in USA, not in many other countries.

Okay; that statement is still in the Apple doc, and without qualification… And equivalent text is shown in US, UK, and Spain.

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require higher security.

Newly-created Apple IDs get two factor and cannot disabled it, when that new Apple ID is created through some of the various of the available paths. The number of those paths has been being reduced over time, too—and I have’t recently checked to see if it’s now required on all creation paths.

Apple has been pushing everybody firmly toward two-factor, and which is useful for protecting against phishing, and password cramming secondary to password re-use, and other commonplace attacks.

I expect we’ll see token-based two factor support arriving fairly soon too, particularly given the integrated support for two-factor authentication in iOS and iPadOS 15.

By all means, yes, have two-factor enabled.

But AFAIK, we’re not quite completely at endemic two-factor requirements. Yet.

two factor authentication is a requirement of having an icloud account with an iphone

You cannot disable it.

"...If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings. ..."

Maybe in USA, not in many other countries.

Thank you for teaching me something new!

Thank you, I’ll go back to my original advice.

I have set up three active AppleIDs in UK and never had that opportunity. It was only when the ID was used to sign into an Apple device that 2FA was invoked with no grace period and no email.

In any case it is totally crazy not to use 2FA as I think we all agree.