How to Optimise Interaction to Next Paint (INP)?

Interaction To Next Paint (INP) issues could happen on Consent Notices UI Interactions, especially on Mobile devices. 📱

What can developers and 3P (CMPs) do to optimise this critical user experience flow?

Optimising long tasks is crucial for enhancing the user experience, especially during interactions with Cookie Consent UIs on mobile devices. Here's how developers and third-party Consent Management Platforms (CMPs) can optimise this critical user experience flow:

1. Understand tasks and the main thread: Tasks are discrete pieces of work like rendering and running JavaScript. The main thread, which runs most tasks, can only process one task at a time. Long tasks over 50 ms cause interaction or render latency​​.

2. Breaking up long tasks: Convert long tasks into smaller ones, which allows the browser to handle higher-priority work like user interactions more efficiently​​.

3. Deferred execution: Use setTimeout() to defer less critical tasks, thus freeing the main thread to handle user-facing work immediately​​.

4. Yielding to the main thread: Employ async/await to create yield points for crucial user-facing tasks. This approach breaks up monolithic tasks into separate, smaller ones, improving responsiveness​​.

5. Responding to user interactions: Utilize isInputPending() to yield to the main thread during user interactions, ensuring that tasks don't block important user-facing processes​​.

6. Prioritise with the scheduler API: Use the postTask() function for finer-grained scheduling of tasks, prioritizing critical tasks over background ones​​.

7. Built-in yield with continuation: Implement scheduler.yield for a continuation mechanism, ensuring that after yielding, tasks resume in the order they were scheduled​​.

8. Limit work in each function: Do as little work as necessary in functions to minimize the impact on the main thread and improve the ability to handle user interactions quickly​​.

Image Credit: Gilberto Cocchi

Below is an example of how much INP could be improved if developers would yield on consent update callbacks. It would be even better if the CMPs would do the same via Click Emit Handlers, Yielding on Callback triggers, etc.

Image Credit: Gilberto Cocchi

By incorporating these strategies, developers and CMPs can significantly improve interaction to the next paint (INP), providing a smoother and more responsive experience for mobile users when they engage with cookie consent prompts or other interactive elements on a webpage.

Learn more information about the different Yield methodologies in the below article. 🔗

Optimize long tasks | Articles | web.dev

You've been told "don't block the main thread" and "break up your long tasks", but what does it mean to do those things?

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