INP and Core Web Vitals in practice

A page can show its first content quickly yet react slowly to a click. Performance checks therefore extend beyond initial loading to tasks users perform later.

What INP helps assess

INP describes responsiveness during interactions such as clicks, taps and keyboard input. Diagnosis starts with specific actions that feel slow rather than improvements to an arbitrary piece of code.

Documentation: web.dev.

Start with a scenario

Opening a menu, adding a product or expanding filters can provide a test case. We record the device, conditions and when the delay occurs. A single test cannot represent the experience of every user.

Find work delaying the response

We examine calculations, view updates and scripts running during the interaction. A change should remove unnecessary work or improve its sequencing. Adding a waiting animation alone does not address the cause.

Example: a complex filter

If selecting one option recalculates the full list several times, we investigate the repetition. After the change, we test response speed and result accuracy. Faster filtering is not a success if products disappear incorrectly or data becomes stale.

Review and ongoing checks

We compare the same scenario before and after the change, then observe available real-use data. Test conditions are documented. New scripts, components and integrations should also be assessed for their impact on interaction.