The answer to 'are spider dangerous' is that most spiders are not dangerous to humans. While some spiders can deliver a painful bite, the vast majority of spider species found in homes are not considered medically significant. Spiders are generally more afraid of humans and will avoid confrontation if possible.
The exceptions are a few venomous spider species, like the black widow and brown recluse, which can deliver a potentially dangerous bite. However, even these spiders are not aggressive and will only bite in self-defense if directly threatened or handled. Bites from these spiders are rare and can usually be treated effectively with proper medical care.