You can track all registered post which is handled by An Post through their website and their tracking accuracy has improved as the service has developed since its founding in the 1980s. However, tracking using the An Post website is not advisable when it comes to international parcel tracking as often parcels will be handed over to other couriers or logistics companies when on their way into and out of Ireland.
To track An Post parcels worldwide, particularly when using the An Post EMS service, using the multi-tracking platform Ship24 is your best bet. From the Ship24 website, you can find all your An Post tracking needs with just your An Post tracking number.