Max Potential First Input Delay (Max Potential FID) [beta]
Collected from: Web Browser (API) + approximation
The Max Potential First Input Delay (Max Potential FID) is the worst value a First Input Delay could have. First Input Delay (FID) is the delay a user experiences when interacting with the page for the first time (example: delay to get a feedback from the page when clicking an element). The FID is depending on the page busyness (tasks preventing responsiveness) and on when the user interacts. Indeed, a user can be lucky and interact when the page is responsive (no treatment being processed by the browser)… or not.
Max Potential First Input Delay (max FID) is the theoretical maximum delay a user could experience when interacting with a page, whatever is the considered moment for the interaction.
Whereas the FID is collected from a given interaction of a real user, the Max Potential FID can be computed without a user, the value is the delay that a user would face by interacting with the page when the page is least responsive (worst case scenario).
Max Potential First Input Delay is computed by finding the longest task after the First Contentful Paint (as we can consider a user would not attempt to interact with a page before any content being displayed).
Max Potential FID is available as a beta metrics on Dareboost as we’re offering an approximation for some web pages. If no long tasks (no browser task of more than 50 ms) are detected when loading a page, Dareboost considers the Max Potentiel FID is 40 ms. It could actually be any value between 0 and 50 ms.