INP (Interaction to Next Paint)
Definition
Interaction to Next Paint (INP) measures how quickly a page responds visually after a visitor taps, clicks, or types, based on the slowest typical interactions across the whole visit. Google's good threshold is 200 milliseconds or less at the 75th percentile. It replaced First Input Delay in 2024 and reflects responsiveness throughout the visit, not only the first click.
Why it matters for your store
Shopping is a series of interactions: open the size menu, add to cart, open the cart, change a quantity, go to checkout. If each one lags for half a second, the store feels broken even when it is fast to load. Visitors tap again, add two items by mistake, or leave.
INP is mostly a JavaScript problem. The more script a page runs, the more often the main thread is busy when the visitor taps. Third-party tags for analytics and advertising are frequent offenders because they run on every page and are rarely measured. The fix is less script, script that runs off the main thread, and interfaces that show a response immediately and finish the work afterwards.
How Kambloo handles it
Kambloo's storefront budget sets INP under 200 milliseconds and caps total JavaScript at 90 KB compressed, of which the platform's own interactive layer uses under half. Themes cannot exceed the remainder, and the check runs before a theme is accepted.
Interactive elements such as the cart drawer show a loading state at once and update when the server responds, so the visible reaction is immediate. Heavy work is moved to background queues rather than done in the request. Third-party scripts for analytics and advertising are deferred or run through a worker so they do not block the main thread.
Real-user INP is collected per store and reported in the SEO health report alongside LCP and CLS.
Questions about INP (Interaction to Next Paint)
What makes INP slow on a store?
Heavy JavaScript running on the main thread: large frameworks, third-party tracking scripts, and interactions that do a lot of work before updating the screen. Fewer scripts and immediate visual feedback fix most of it.
Does INP include the time to complete an action such as adding to cart?
No. It measures the time until the screen visibly responds, not until the server finishes. Showing a loading state immediately keeps INP low even if the server takes longer.