Why does my MacBook Air slow down with too many tabs open?

Your MacBook Air likely has 8GB of RAM, and each tab uses 50–100MB. Stacking 30+ tabs eats 3GB+ just for tabs, leaving almost nothing for Safari after the OS uses 4GB. This forces swapping to the slower SSD. Close tabs you don’t need, use a session manager like OneTab, or limit open tabs to under 20.