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What Is an AnimationFrame and What Can It Tell You?

Front End Lead at Gilion, previously Spotify and Klarna

Modern web applications need to be responsive and smooth, providing users with immediate feedback for their interactions. To understand how well our applications perform, we need to understand how browsers process and render content. This is why we now have AnimationFrames, a new representation of unit of work that powers INP and LoAF APIs!

This talk has been presented at JSNation 2025, check out the latest edition of this JavaScript Conference.

FAQ

Vinicius's talk focuses on animation frames and the Long Animation Frame API (LOAF), exploring how they can help improve web application performance and user experience.

Vinicius is a lead engineer at PlusOne and is involved in building PerfLab and PerfAgent.

Animation frames are crucial for understanding how browsers process and render content, helping developers create smooth and responsive web applications by measuring work needed to present new frames.

The Long Animation Frame API (LOAF) is an API that helps developers identify bottlenecks in their web applications by exposing animation frame entries that exceed a 50-millisecond threshold.

The INP score consists of input delay, processing time, and presentation delay, which are measured within animation frames to assess user interaction performance.

Animation frames provide a framework for measuring and classifying work needed to present a frame, offering insights into user interactions and helping improve web performance.

The Long Task API's attribution model fails to provide detailed insights into which scripts or functions are causing long tasks, offering only timestamps and blocking duration.

Developers can analyze performance issues by capturing and examining trace files, utilizing tools like the Long Animation Frame API and Web Vitals, and leveraging AI-assisted analysis for better insights.

Recommended tools include the Long Animation Frame API, Web Vitals for real user monitoring, and self-profiling APIs for capturing traces.

As of now, the Long Animation Frame API is supported in Chrome and other Chromium browsers like Edge, with Safari working on implementation.

performance

Vinicius Dallacqua

29 min

12 Jun, 2025

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Video Summary and Transcription

Vinicius discusses the importance of smooth and responsive web applications, focusing on animation frames and the long animation frames API. Understanding work within frames is crucial for user experience and INP metrics. Categorizing animation frame work helps in performance analysis, specifically in identifying issues with layout and rendering. Attribution models and IMP metric play a significant role in performance analysis using animation frames. Leveraging animation frames for bottleneck detection and visualization of work execution on the main thread is essential for performance optimization.

Available in Español: ¿Qué es un AnimationFrame y qué puede decirte?

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