The characteristics of an original licence
- The key format. An original Microsoft key consists of 25 alphanumeric characters, split into five groups of five, separated by hyphens.
- The complete scope of delivery. An original licence includes not just the key, but also a way to obtain the matching, Microsoft-signed setup file.
- The proof of purchase. A VAT invoice documents the lawful acquisition and is part of every properly sold licence.
- The successful activation. The ultimately decisive characteristic: Microsoft's server accepts the key and lists the software as original.
What does not define an original key
An original licence is not recognised by fancy packaging or a glossy card. With the electronic delivery that is common today, there is no physical medium; the key arrives by email. That is not a shortcoming, but the standard.
And a low price is no sign of a counterfeit. An original, previously used licence may be cheaper than new goods; this is the principle of exhaustion. What matters is not the price, but the combination of correct format, complete scope of delivery, proof of purchase and successful activation.