How can I know if my AirPods are original?

Purchased from a local market - they in all likelihood are not genuine.

Counterfeits can be very convincing (cosmetically speaking) and can include known-good serial numbers.

Your best indicators will poor audio performance, non-functioning features, or an “unable to verify” message from iOS.

If you want “genuine” … you need to purchase from Apple - or an authorized reseller - and break the tamper-evident packaging seals yourself.