angular-errors

name	angular-errors
description	Troubleshooting guide for Angular runtime and compiler errors with per-code reference docs.
license	MIT
metadata	{"author":"Copyright 2026 Google LLC","version":"1.0"}

Angular Error Troubleshooting Guide

Use this skill when Angular reports an NGxxxx error code and you need fast root-cause and fix guidance.

Recommended Workflow

1. Identify the exact error code (NG0100, NG8002, etc.) from terminal or browser console.
2. Determine whether it is a runtime or compiler error.
3. Open the corresponding file in references/ (for example references/NG0201.md).
4. Apply fixes from the sections: Why this error happens, How to debug, and How to fix.
5. Re-run your app/tests and verify the error is resolved.

Runtime Errors

Runtime errors occur while your application is running. This section summarizes common Angular runtime errors.

Code	Name
NG0100	Expression Changed After Checked
NG01101	Wrong Async Validator Return Type
NG01203	Missing value accessor
NG0200	Circular Dependency in DI
NG0201	No Provider Found
NG0203	inject() must be called from an injection context
NG0204	Invalid Injection Token
NG0205	Injector has already been destroyed
NG0207	EnvironmentProviders in wrong context
NG0209	Invalid multi provider
NG02200	Missing Iterable Differ
NG02800	JSONP support in HttpClient configuration
NG02802	Headers not transferred by HttpTransferCache
NG0300	Selector Collision
NG0301	Export Not Found
NG0302	Pipe Not Found
NG0401	Missing Platform
NG0403	Bootstrapped NgModule does not specify a root component
NG0500	Hydration Node Mismatch
NG05000	Hydration with unsupported Zone.js instance
NG0501	Hydration Missing Siblings
NG0502	Hydration Missing Node
NG0503	Hydration Unsupported Projection of DOM Nodes
NG0504	ngSkipHydration flag is applied to an invalid node
NG0505	No hydration info in server response
NG0506	Application remains unstable
NG0507	HTML content was altered after server-side rendering
NG0602	Disallowed function call inside reactive context
NG0750	@defer dependencies failed to load
NG0751	@defer behavior when HMR is enabled
NG0910	Unsafe bindings on an iframe element
NG0912	Component ID generation collision
NG0913	Runtime Performance Warnings
NG0919	Circular Dependency Detected
NG0950	Required input is accessed before a value is set
NG0951	Child query result is required but no value is available
NG0955	Track expression resulted in duplicated keys for a collection
NG0956	Tracking expression caused re-creation of DOM structure

Compiler Errors

Compiler errors occur when the Angular compiler fails to process your code, usually due to syntax or structural issues. This section summarizes common Angular compiler errors.

Code	Name
NG1001	Argument Not Literal
NG2003	Missing Token
NG2009	Invalid Shadow DOM selector
NG3003	Import Cycle Detected
NG6100	NgModule.id set to module.id anti-pattern
NG8001	Invalid Element
NG8002	Invalid Attribute
NG8003	Missing Reference Target

Detailed per-code guidance is available in references/NGxxxx.md files.

If you need additional framework context, use the official Angular Errors guide.