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I'm a bit confused on the uniqueness of each passive RFID tag.. are they unique globally?

Meaning, every RFID manufacturer (no matter if based in USA, China or India) never creates a tag with the same unique id?

So if I buy a batch of China Generation 1 Class 0 RFID tags and then buy another batch of Generation 1 Class 0 RFID tags from India, I'm sure that the Generation 1 Class 0 RFID tags' UID will never collide?

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No, they're not globally unique, they're unique per manufacturer. For one thing, not all manufacturers use the same code length. If I want to start producing RFID tags tomorrow I can do whatever I please to do, like producing two RFIDs for every code, or even produce a whole batch with the same code. If you want to have them unique, you'll have to stick to one manufacturer.
That said, the codes are pretty long, so chances are slim that you'll have two colliding codes.

In the (near?) future RFIDs are going to replace bar codes in logistics. Those will have a combination of a non-unique product code, like EPC (European Product Code) and a unique ID.

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  • \$\begingroup\$ Wouldn't different code lengths make the codes effectively more unique? \$\endgroup\$
    – Federico Russo
    Jul 5, 2011 at 6:39
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    \$\begingroup\$ @Federico - Logically, yes. But the point is that the different code lengths origin from a lack of standards, and standardization is required for global uniqueness. My impression is that now there's more work being done towards standards, but there are a lot of them, including dozens of sub-standards. An inheritage from the past, me thinks. The field still looks messy. \$\endgroup\$
    – stevenvh
    Jul 5, 2011 at 6:49
  • \$\begingroup\$ Apparently there is a registry for gen 2 tags: rfidjournal.com/expert/entry/8523 \$\endgroup\$
    – Casebash
    Feb 28, 2013 at 2:08

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