Angular DevTools

Inspect Angular component trees, signals, dependency injection, and routes — at dev time, build time, or through a coding agent. Built with Devframe so the same tool runs as an embedded panel, standalone CLI, static report, MCP server, or Chrome DevTools extension.

Features

• Component inspector — discover components, inputs, outputs, and source files; view injected providers per component
• Signal graph — visualize signal, computed, linkedSignal, effect nodes and their dependency edges (Angular 19+)
• DI inspector — browse the injector hierarchy (element and environment) with providers at each level (Angular 17+)
• Route inspector — list registered routes from source
• NgRx Store inspector — detect @ngrx/store (actions, reducers, effects, selectors) and @ngrx/signals (signalStore, signalState, signalMethod) patterns from source; live state & action log via Redux DevTools protocol
• Forms inspector — every form on the page (Signal Forms, reactive and template-driven) with each field's value, status, touched/dirty state and readable errors, plus a timeline of recent changes; hover a field to highlight its input
• Build metadata — Angular version, TypeScript version, SSR status
• In-page popup — floating devtools panel with dock modes (float, bottom, right), drag, resize, and localStorage persistence
• Agent-native — all inspectors exposed as MCP tools and resources
• Deep linking — URL hash navigates to a specific tab (#tab=signals)
• Page overlay — highlights components in the running app

Install

npm install @santoshyadavdev/ng-devtools devframe

MCP agent support (@devframes/agentic) is included.

How to Use

Embedded in an Angular app (Express SSR)

Add the devframe middleware to your Express server:

// server.ts
import { initDevframe } from 'devframe/initiate';
import ngDevtools from '@santoshyadavdev/ng-devtools/devframe';

const devtools = initDevframe(ngDevtools, { base: '/__ng-devtools/' });
app.use(devtools.nodeMiddleware);

Open http://localhost:4000/__ng-devtools/ to see the devtools UI.

Standalone CLI

# Dev server with live RPC
npx @santoshyadavdev/ng-devtools dev

# Static report (offline HTML)
npx @santoshyadavdev/ng-devtools build --outDir dist-report

# MCP server for coding agents
npx @santoshyadavdev/ng-devtools mcp

MCP Server for Coding Agents

Claude Desktop — add to claude_desktop_config.json:

{
  "mcpServers": {
    "ng-devtools": {
      "command": "npx",
      "args": ["@santoshyadavdev/ng-devtools", "mcp"]
    }
  }
}

VS Code — add to .vscode/mcp.json:

{
  "servers": {
    "ng-devtools": {
      "command": "npx",
      "args": ["@santoshyadavdev/ng-devtools", "mcp"]
    }
  }
}

When embedded in Express, the MCP endpoint is also available over HTTP at /__ng-devtools/__mcp.

Agent Tools

MCP clients see these with an underscore, as ng-devtools_get-routes.

Tool	Description
ng-devtools:get-routes	List Angular routes from source
ng-devtools:get-components	Discover components and directives, with inputs and outputs
ng-devtools:get-signals	Signal declarations from source
ng-devtools:get-providers	DI providers from source
ng-devtools:build-meta	Angular/TS versions, SSR status
ng-devtools:highlight	Highlight a component in the page
ng-devtools:inspect-signals	Signal graph a connected page reported
ng-devtools:inspect-providers	Injector tree a connected page reported
ng-devtools:get-ngrx-store	Scan source for NgRx store patterns
ng-devtools:inspect-forms	Forms on the page with every field's state and errors
ng-devtools:explain-form-invalid	Which fields make a form invalid, and why

Forms

The Forms tab and the forms tools read Signal Forms, reactive forms and template-driven forms from the running page, in development builds only. Signal Forms need Angular 21 or later. The live change timeline for reactive and template-driven forms uses control.events (Angular 18+); on Angular 17 changes are picked up every few seconds instead, without submit and reset events.

• Each field shows its value, status, touched/dirty state and errors, plus: Signal Forms constraints (min, max, minLength, maxLength, pattern), a pending debounce, submitting, and disabled reasons; for reactive and template-driven forms, whether validators and async validators are attached, the value reset() goes back to, updateOn, and the bound ControlValueAccessor.
• ng-devtools:explain-form-invalid is the tool to reach for first: without arguments it lists every form that is invalid or waiting on async validation, with each failing field's current value, the validator that failed, its message and whether it was touched. Pass form (an id like form-1, or part of a label like SignupComponent) to explain one form.
• ng-devtools:inspect-forms lists the forms with their status and error counts. Pass form for a field tree, plus path (e.g. address.city), onlyInvalid or includeValues: false to narrow it down.
• Both tools note when the page last reported, so an agent can tell when the data is stale.

Form values leave the page: they are sent to the devtools server, shown in the Forms tab and returned to agents. Values of password fields, fields with a password, one-time-code or credit-card autocomplete, and fields whose name looks secret (password, token, card, cvv and similar) are replaced with [redacted]. Other values are sent as they are, so keep real credentials out of forms you inspect, and don't expose the dev server beyond localhost.

Agent Resources

Resource	Content
ng-devtools:component-tree	Live component hierarchy
ng-devtools:signal-graph	Signal dependency graph
ng-devtools:injector-tree	DI injector hierarchy
ng-devtools:ngrx-store	Live NgRx state & action log
ng-devtools:forms	Live forms and recent changes

Vite DevTools Dock

Mount as a dock panel inside Vite DevTools:

// vite.config.ts
import { viteDevframeHub } from '@devframes/vite/hub';
import { createUi } from '@devframes/hub-ui';
import ngDevtools from '@santoshyadavdev/ng-devtools/devframe';

export default defineConfig({
  plugins: [
    viteDevframeHub({
      devframes: [ngDevtools],
      ui: createUi({ branding: { productName: 'Angular DevTools' } }),
    }),
  ],
});

Chrome DevTools Extension

See the Chrome Extension section below for how to package this as a Chrome extension.

Browser Overlay

The overlay runs inside the user's Angular page and collects live component, signal, DI, and NgRx data. Importing the module starts it, so in most apps that import is all that is needed:

import '@santoshyadavdev/ng-devtools/overlay';

It looks for the devframe connection next to the page and then at /__ng-devtools/.

initOverlay is exported for a devtools mounted somewhere else. Importing the module has already started an overlay on the default URLs by then, so dispose of that one before starting another, or the page ends up with two connections and two polling intervals:

import { initOverlay } from '@santoshyadavdev/ng-devtools/overlay';

const dispose = await initOverlay({ baseURL: '/__my-devtools/' });

In-Page Popup

The devtools can appear as a floating popup directly on your page — no browser extension needed:

import { createDevtoolsPopup } from '@santoshyadavdev/ng-devtools/popup';

createDevtoolsPopup();

This adds a purple FAB button (bottom-right) that opens the full devtools UI in an iframe. Supports three dock modes (float, bottom, right), dragging, resizing, and persists position via localStorage. The popup is automatically loaded in development when using the demo app.

Demo App

The repository includes a demo Angular app (src/) that showcases the devtools with a product catalog built using @ngrx/signals:

• Home — simple counter with signal()
• Products — product list and detail pages powered by a signalStore with withState, withComputed, and withMethods
• About — static page

Run pnpm start and click the purple FAB button to open the devtools popup and see all inspectors in action.

Development

# Install dependencies
pnpm install

# Dev server for the devtools UI (with live RPC)
pnpm devtools:dev

# Build the devtools UI SPA
pnpm devtools:build

# Build the publishable package (library + UI in dist/)
pnpm devtools:build-pkg

# Run the Angular host app (builds the package first, includes in-page devtools popup)
pnpm start

Publishing

The devtool ships as one npm package, @santoshyadavdev/ng-devtools: Node-side logic, RPC, CLI, overlay, popup, and the built UI in dist/public.

# Builds on prepack, then publishes
pnpm devtools:publish

Chrome DevTools Extension

To distribute this as a Chrome DevTools extension, you need a thin Chrome extension shell that opens the devtools UI in a DevTools panel. The built SPA already works standalone — the extension just embeds it.

1. Create the extension scaffold

Create an extension/ directory:

extension/
  manifest.json
  devtools.html
  devtools.js
  panel.html

2. extension/manifest.json

{
  "manifest_version": 3,
  "name": "Angular DevTools",
  "version": "0.0.1",
  "description": "Inspect Angular components, signals, DI, and routes.",
  "devtools_page": "devtools.html",
  "permissions": ["scripting"],
  "host_permissions": [
    "http://localhost/*",
    "https://localhost/*",
    "http://127.0.0.1/*",
    "https://127.0.0.1/*"
  ],
  "icons": {
    "128": "icon-128.png"
  }
}

3. extension/devtools.html and extension/devtools.js

<!-- devtools.html -->
<!doctype html>
<script src="devtools.js"></script>

// devtools.js — creates the panel in Chrome DevTools
chrome.devtools.panels.create('Angular', 'icon-128.png', 'panel.html');

4. extension/panel.html

This is where the built SPA loads. Copy the built assets (dist/devtools-ui/) into the extension and point panel.html at the SPA's index.html:

<!-- panel.html — the devtools SPA loads here -->
<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
  </head>
  <body>
    <iframe src="ui/index.html" style="width:100%;height:100vh;border:none;"></iframe>
  </body>
</html>

5. Build the extension

# Build the devtools SPA
pnpm devtools:build

# Copy into the extension
mkdir -p extension/ui
cp -r dist/devtools-ui/* extension/ui/

6. Load in Chrome

1. Go to chrome://extensions
2. Enable Developer mode
3. Click Load unpacked → select the extension/ directory
4. Open DevTools on any Angular app → the Angular panel appears

7. Publish to Chrome Web Store

1. Zip the extension/ directory
2. Go to the Chrome Developer Dashboard
3. Click New item → upload the zip
4. Fill in the listing details and submit for review

Connecting the extension to the running app

The extension panel loads the SPA in static mode by default. To connect it to a live dev server for real-time RPC, the extension's content script or background service worker needs to detect the devframe's __connection.json on the inspected page and pass the connection to the panel. This is the same pattern the official Angular DevTools Chrome extension uses — a content script bridges the inspected page and the DevTools panel via chrome.runtime.connect.

License

MIT