Time to Interactive
ELI5 — The Vibe Check
Time to Interactive is when your page stops being a beautiful painting you can't touch and actually starts responding to clicks. It's the difference between a wax museum and a real person — looks great, but can I poke it and get a reaction?
Real Talk
Time to Interactive (TTI) measures the time until the page is visually rendered and capable of reliably responding to user input within 50ms. It requires the main thread to be idle for at least 5 seconds after the last long task. It's a key metric for perceived responsiveness.
When You'll Hear This
"The page looks loaded but TTI is 8 seconds because of all that JavaScript parsing" / "Code splitting brought our TTI down by 40%"
Related Terms
First Paint
First Paint is the moment your browser stops showing a blank white screen and puts literally anything on it.
Long Tasks API
The Long Tasks API is a snitch that tells you whenever JavaScript hogs the main thread for more than 50 milliseconds.
Total Blocking Time
Total Blocking Time is the sum of all the moments your browser was too busy running JavaScript to notice you desperately clicking buttons.