Here’s something that doesn’t get talked about enough: your React app can have great LCP and FCP scores, pass all your Lighthouse checks, and still feel sluggish to use. The culprit is usually Long Tasks. What’s a Long Task? The browser’s main thread handles everything — parsing HTML, running JavaScript, responding to user input, painting pixels. It can only do one thing at a time. A Long Task is any task that occupies the main thread for more than 50 milliseconds without a break. While a Long Task is running, the browser can’t respond to anything else. Click a button during a Long Task? Nothing happens — until the task finishes. ...

If you’ve seen the term “Core Web Vitals” and kept scrolling, this article is for you. It’s not just SEO jargon. These three metrics are the clearest signal we have for whether a web app feels fast to a real user — and they’re measurable directly from your React code. This article covers what the three metrics actually mean, how to measure them without any external tools, and what to do when they’re bad. ...

Monitoring and Alerting Are Different Jobs. Most React Teams Only Have One. Tags: #react #performance #webdev #javascript Tuesday you deploy. Thursday your LCP climbs from 1.2s to 2.8s. Friday the reviews start coming in. Your monitoring dashboard shows the spike clearly — it just waited until you opened it to tell you. That’s the gap. Not a tooling failure exactly. More of a category error. What monitoring tools are actually built for Datadog, New Relic, your APM of choice — these are built for historical analysis. What happened over the past week, which pages are consistently slow, where the backend bottlenecks are. That’s genuinely useful work, and they do it well. ...

Welcome to the RPAlert blog. This is where we’ll share insights on web performance monitoring, practical tips for improving Core Web Vitals, and updates on RPAlert. What to expect Web Performance — How to measure and improve LCP, INP, and CLS in production Using RPAlert — SDK integration guides and best practices Product Updates — Release notes and changelog highlights Stay tuned.