Is the iPhone I bought through the online marked covered by Apple’s worldwide warranty?

I bought a device through the online market

Which one? There are more than one on the Internet.

In most territories - and you didn't say where you are - warranties require only a sales receipt which you must have received in the transaction.

If you are in doubt always check you coverage at Apple's page Check Your Service and Support Coverage. Enter your serial number of your device (iPhone?) which you can capture at Settings > General > About. See Find the serial number of your Apple product and specifically this page for iPhone.

Apple has more to say on warranty coverage in Correct the purchase date or expiration date for your AppleCare agreementApple Support.

Tranhuyhuy wrote:

Thank you! So the warranty is useless for my device, why should apple do that to users?

Because iPhone is not the same in every country. iPhone is manufactured by region sold. Apple's policy is if there is a warranty issue where the phone has to be replaced, it has to be replaced with the exact model purchased. A phone purchased in the United States, is different from a phone purchased in Viet Nam. As such if a phone purchased in the US, requires replacement in another country, that country will not have an exact replacement model. Thus the warranty for iPhone is not now, nor has it ever been international.

There is no “worldwide warranty” on iphones. There never has been. The warranty is only valid in the country where the device was originally sold.

Asking why questions can't be answered here. Apple has maintained this warranty on iPhone since the dawn of iPhone. It is always advised to purchase your iPhone in the country you live and will be used in.

Otherwise, we are all users here on this user to user only forum and we have nothing to do with Apple warranties or their enforcement.