: The software checks the key against the developer's server every time it starts. If a key is flagged as public or "blacklisted," the software reverts to the free version.
Some users buy the software, extract the license key, request a refund, and then try to use the key offline. Developers check refunded keys. They will blacklist your key within 24-48 hours. This is a short-term trick that ultimately fails. vdownloader plus license key new