TTI generally stands for Time to Interactive, and refers to the time until a web page is not merely "visually
rendered" but has reached a stable state where it can reliably respond to user interactions such as clicks and input.
A: Common causes include: heavy or excessive JavaScript (long main-thread time), too many third-party tags (GTM, analytics, ads, chat, etc.), and many scripts running on initial load that delay input handling. Another reason is usually heavy content like images not being optimized for web.