https://github.com/edisonaugusthy/angular-render-scan
Angular Render Scan is a visual debugging overlay for Angular change detection.
https://github.com/edisonaugusthy/angular-render-scan
Last synced: 1 day ago
JSON representation
Angular Render Scan is a visual debugging overlay for Angular change detection.
- Host: GitHub
- URL: https://github.com/edisonaugusthy/angular-render-scan
- Owner: edisonaugusthy
- License: mit
- Created: 2026-05-24T13:16:37.000Z (24 days ago)
- Default Branch: main
- Last Pushed: 2026-06-04T11:07:38.000Z (13 days ago)
- Last Synced: 2026-06-04T12:10:54.532Z (13 days ago)
- Language: TypeScript
- Homepage: https://www.npmjs.com/package/angular-render-scan
- Size: 11.6 MB
- Stars: 4
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- fucking-awesome-angular - angular-render-scan - A visual debugging overlay for Angular change detection. (Development Utilities / Debugging)
- awesome-angular - angular-render-scan - A visual debugging overlay for Angular change detection. (Development Utilities / Debugging)
README
# Angular Render Scan
Angular Render Scan is a visual debugging overlay for Angular change detection. It shows which components update, how often they update, and which checks are slow or wasted.
[Live Demo](https://edisonaugusthy.github.io/angular-render-scan/) | [npm](https://www.npmjs.com/package/angular-render-scan)
## Versions
| Package | Version |
| ------------------------- | --------- |
| Angular | `^22.0.0` |
| `angular-render-scan` | `0.1.8` |
| `angular-render-scan-cli` | `0.1.5` |
## What it shows
- Component render outlines and heatmap colors.
- Slow render and budget violation alerts.
- Change detection trigger labels such as `zone:click`, `signal:write`, and `router:navigation`.
- OnPush candidates, referentially unstable inputs, and suspected Zone pollution.
- A copyable AI performance prompt for slow/error components.
- Session export JSON for deeper debugging.
## Install
```sh
npm install angular-render-scan
```
Angular Render Scan expects Angular 9+.
## Setup with the CLI
```sh
npx angular-render-scan-cli init
```
The CLI supports Angular CLI and Nx workspaces. It looks for `angular.json`, `workspace.json`, `nx.json`, or `project.json`, finds your `main.ts` or `app.config.ts`, and adds `provideAngularRenderScan()`.
```sh
npx angular-render-scan-cli init --dry-run
npx angular-render-scan-cli init --script-tag
npx angular-render-scan-cli --help
```
## Manual Setup
Add the provider to your Angular bootstrap config.
```ts
import { bootstrapApplication } from "@angular/platform-browser";
import { provideAngularRenderScan } from "angular-render-scan";
import { AppComponent } from "./app/app.component";
bootstrapApplication(AppComponent, {
providers: [
provideAngularRenderScan({
enabled: true,
animationSpeed: "fast",
}),
],
});
```
For script-tag usage:
```html
```
Provider mode is recommended for Angular component-level instrumentation.
## Common Options
```ts
provideAngularRenderScan({
enabled: true,
showToolbar: true,
showFPS: true,
animationSpeed: "fast",
maxLabelCount: 20,
maxRecordedCycles: 30,
showCopyPrompt: true,
promptContext: "Angular app using signals and OnPush components",
log: false,
});
```
Useful options:
- `enabled`: turns scanning on or off.
- `showToolbar`: shows the floating toolbar.
- `animationSpeed`: `'fast'`, `'slow'`, or `'off'`.
- `showFPS`: shows FPS in the toolbar.
- `log`: prints cycle summaries to the console.
- `include` / `exclude`: limits which components are tracked.
- `minDurationMs` / `minRenderCount`: filters low-signal entries.
- `maxRecordedCycles`: controls how much history is included in copied prompts.
- `promptContext`: adds app-specific context to copied prompts.
- `dangerouslyForceRunInProduction`: allows scanner runtime outside Angular dev mode.
## Runtime API
```ts
import {
copyAIPrompt,
getAIPrompt,
getCdGraph,
getOnPushCandidates,
getOptions,
getReferentialInstability,
getZonePollutionEvents,
scan,
setOptions,
stop,
} from "angular-render-scan";
scan();
setOptions({ enabled: false });
setOptions({ enabled: true, log: true });
console.log(getOptions());
console.log(getAIPrompt());
await copyAIPrompt();
console.log(getOnPushCandidates(40));
console.log(getReferentialInstability(1));
console.log(getZonePollutionEvents());
console.log(getCdGraph());
stop();
```
## Toolbar
The toolbar shows render count, FPS, latest cycle time, slowest component, trigger source, OnPush candidates, Zone pollution events, alerts, and copy/export actions.
Useful shortcuts:
| Shortcut | Action |
| ------------- | -------------------------- |
| `Alt+Shift+S` | Toggle scanner |
| `Alt+Shift+D` | Toggle Details Mode |
| `Alt+Shift+C` | Copy AI performance prompt |
| `Alt+Shift+X` | Clear stats |
| `Alt+Shift+T` | Toggle toolbar |
| `Escape` | Close open panels |
## Details and AI Prompt
Enable `Details` in the toolbar, hover a captured component, then click it to pin a recommendation panel. The panel shows timing, render count, reason, selector, changed inputs, recent cycles, and local Angular recommendations.
Use `Copy Slow Issues Prompt` to copy a focused prompt for an AI coding assistant. It includes recent cycle history, thresholds, and slow/error component evidence without copying DOM nodes, component instances, or source code.
## Playwright Audit
```ts
import { test, expect } from "@playwright/test";
import { startRenderAudit } from "angular-render-scan";
test("no render regression", async ({ page }) => {
await page.goto("/");
const audit = await startRenderAudit(page);
await page.click("button.expensive-operation");
const report = await audit.stop();
expect(await report.maxDurationFor("ProductCardComponent")).toBeLessThan(
16.7,
);
expect(await report.wastedRenderPercentage()).toBeLessThan(20);
expect(await report.budgetViolations()).toHaveLength(0);
});
```
## Production Behavior
Angular Render Scan is intended for development and demo debugging. Provider mode checks Angular `isDevMode()` and does not run in production unless explicitly enabled.
```ts
provideAngularRenderScan({
dangerouslyForceRunInProduction: true,
});
```
Use that option carefully. The scanner adds runtime instrumentation, DOM reads, canvas work, and debug behavior.
## Demo
Hosted demo:
```txt
https://edisonaugusthy.github.io/angular-render-scan/
```
Local demo:
```sh
npm install
npm run dev
```
Open `http://127.0.0.1:4200/`.
## Development
```sh
npm run test
npm run build
npm run test:e2e
```
## Release
Release runs automatically on pushes to `main`. The workflow bumps the package version, publishes `angular-render-scan` and `angular-render-scan-cli` to npm, and creates a GitHub release.
Configure `NPM_TOKEN` or npm trusted publishing for both packages before publishing.