Time to Interactive

Time to Interactive (TTI) measures the moment at which the main thread has had 5 seconds with no network activity or JavaScript long tasks.

Why is monitoring Time to Interactive important?

Time to Interactive is influenced by JavaScript main thread activity. Pages that have a large amount of scripting will delay the time to interaction. Scripting performance varies greatly from device to device—slower CPUs spend far more time parsing and compiling, than faster ones.

How is Time to Interactive calculated?

Calibre observes the point at which the main thread activity has no major JavaScript activity. The timeline below illustrates JavaScript activity on the main thread.

Time to Interactive

Major activity is categorised as JavaScript tasks that take longer than 50ms. Calibre works backwards from the time of document completion until it finds a point at which the browser is at rest.

If a user were to interact with the page, there would be notable delay. Each Calibre test has a timeout of 60 seconds, if a page does not become interactive within 60 seconds, the metric will not be recorded for the run. Learn more about Time to Interactive.

What Time to Interactive measurement is fast?

Good TTI MeasurementPoor TTI Measurement
≤ 3.8s> 7.3s

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