Websperre differs from other "website blocking" extensions by generating the unlock key/password by itself.
The blocked websites added by the user only become accessible again if the user removes it from the block list (i.e. there is no timer based unlock system).
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A website blocking extension works best if the block list and access to the block list is separated. So, Websperre generates more than one unlock key and has its own unique system of showing the block list if the user tries to access it. It is intentionally made difficult, but not impossible, to discourage the user from opening a website they had blocked.
A more detailed explanation of how Websperre works can be found at the extension's repository.
