What Is Time to Interactive?
Time to interactive, or TTI, is a metric that records when a page has displayed content and the main thread is free enough to respond to input within a short, consistent delay. It captures the gap between a page looking ready and actually being ready to use. Heavy script execution after paint pushes TTI later.
Why it matters
A page can appear loaded yet ignore taps because scripts are still parsing, which TTI exposes. Reducing main-thread work brings the usable moment closer to the visible one.
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