FCP
A curated list of web performance metrics, tools, and concepts for measuring page speed and user experience.
What is FCP?
Awesome Page Speed Metrics is a curated GitHub repository that serves as a reference guide for web performance measurement. It aggregates definitions, tools, and resources for understanding key metrics like Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and First Input Delay (FID) that impact page speed and user experience. The project helps developers identify what to measure, how to measure it, and which tools to use for both lab and real-user monitoring.
Frontend developers, performance engineers, and web developers who need to measure, analyze, and optimize website performance. It's particularly useful for those implementing performance budgets, monitoring Core Web Vitals, or setting up real-user monitoring (RUM).
It saves time by consolidating scattered performance resources into a single, well-organized reference. Unlike generic documentation, it provides practical code snippets, tool comparisons, and clear metric explanations tailored for immediate implementation.
Overview
⚡Metrics to help understand page speed and user experience
Use Cases
Best For
- Understanding Core Web Vitals and other key performance metrics
- Setting up real-user monitoring (RUM) for web applications
- Comparing lab testing tools like Lighthouse and WebPageTest
- Learning about the critical rendering path and long tasks
- Implementing performance measurement with code snippets
- Finding authoritative resources on web performance standards
Not Ideal For
- Teams seeking an all-in-one performance monitoring platform with automated alerts and dashboards
- Developers who prefer interactive, hands-on tutorials over reference documentation
- Projects focused solely on backend performance without frontend web metrics
Pros & Cons
Pros
Provides detailed explanations of key metrics like LCP, CLS, and FID, with direct links to official W3C specifications and Google's web.dev documentation, making it a reliable reference.
Curates links to both lab tools like Lighthouse and field tools like Web Vitals library, helping users select appropriate measurement methods for synthetic and real-user monitoring.
Includes JavaScript code examples for measuring network timing metrics such as DNS latency and TTFB, facilitating immediate use in projects without extensive research.
Aggregates resources from industry leaders like Google and W3C, saving developers time from scattered research by providing a structured overview of essential performance concepts.
Cons
As a static list, it may not be updated in real-time with the latest tool versions or metric changes, requiring users to verify external links for current information.
The README directs beginners to other resources first, making it less accessible for those new to web performance without additional learning or context.
While it provides snippets and links, it doesn't offer step-by-step guides or project-based examples for comprehensive, hands-on learning beyond measurement basics.
Frequently Asked Questions
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