What kind of spider is this?Watch
Most spiders are not dangerous
Is it dangerous? I saw it crawling around in my house yesterday and thought it was just some dirt on the floor but today I saw it closely and it was a freaking spider, it scared the life out of me at first because it's a lot bigger than it looks.
Assuming you're in the UK, a large spider in a house is just gonna be a Tegenaria species (the house spiders).Worst case scenario, it's a false widow. Those can give a nasty bite if you attack them but you couldn't exactly call them dangerous. The UK has no genuinely dangerous species.
All are fine and wont harm you if you leave them alone