Real-time performance monitoring toolbar for React apps. FPS, jank %, input delay, memory, network, React renders, and hydration timing — all in one zero-config overlay. Inspired by Linear's developer toolbar and built by dylsteck.
https://github.com/user-attachments/assets/f3f2d6c2-c7b6-489d-b869-9a07f978f4c9
// App.tsx or layout.tsx
import { JankMeter } from 'jankmeter/react';
export default function App() {
return (
<>
<JankMeter />
{/* your app */}
</>
);
}
// vite.config.ts
import { jankMeter } from 'jankmeter/vite';
export default {
plugins: [jankMeter()],
};
For callbacks like onMetrics, use init() directly; the plugin only supports serializable config.
// app/layout.tsx
import { JankMeter } from 'jankmeter/next';
export default function RootLayout({ children }) {
return (
<html>
<body>
<JankMeter />
{children}
</body>
</html>
);
}
import { init, destroy, getMetrics } from 'jankmeter';
init({
onMetrics: (m) => console.log(m),
});
// Later: destroy();
| Metric | Source | Browsers |
|---|---|---|
| FPS | requestAnimationFrame rolling window | All |
| Jank % | Dropped frames / expected frames | All |
| Delay | Event Timing API (INP-style) | Chrome 96+ |
| Memory | performance.memory | Chrome only |
| Network | fetch/XHR instrumentation + PerformanceObserver | All |
| React | bippy + DevTools hook | All (with React) |
| Hydration | First commit timing | All (with SSR) |
interface JankMeterConfig {
enabled?: boolean; // default: true
shortcut?: string; // default: 'Ctrl+Shift+M' — supports 'F2', 'Ctrl+Shift+K', etc.
throttleMs?: number; // DOM update interval, default: 500
maxHistory?: number; // sparkline data points, default: 60
onMetrics?: (metrics: AllMetrics) => void;
}
Ctrl+Shift+M by default, configurable (e.g. F2, Ctrl+Shift+K)sideEffects: false)// webpack.config.js
const { JankMeterWebpackPlugin } = require('jankmeter/webpack');
module.exports = {
plugins: [new JankMeterWebpackPlugin()],
};
Requires html-webpack-plugin. Dev mode only — automatically disabled in production builds. For callbacks like onMetrics, use init() directly; the plugin only supports serializable config.
import { getMetrics } from 'jankmeter';
const snapshot = getMetrics();
// { fps, delay, memory, network, react, hydration }
| Browser | FPS | Delay | Memory | Network | React |
|---|---|---|---|---|---|
| Chrome 96+ | Full | Full | Full | Full | Full |
| Firefox | Full | N/A | N/A | Full | Full |
| Safari | Full | N/A | N/A | Full | Full |
| Edge | Full | Full | Full | Full | Full |
See CONTRIBUTING.md for how to contribute.
FAQs
Real-time performance monitoring toolbar for React apps
We found that jankmeter demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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