How to fix Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option in your 'tsconfig' to remove this warning. in TypeScript

What this error means

The "experimentalDecorators" warning appears when TypeScript encounters decorator syntax (@decorator) in your code but the compiler option to enable decorators hasn't been set. Decorators are a special TypeScript feature that allows you to add annotations and metadata to classes, methods, properties, and parameters. TypeScript supports two types of decorators: 1. **Legacy/Experimental Decorators** - The original implementation based on a TC39 proposal that was never standardized. This requires the experimentalDecorators flag. 2. **Standard Decorators** - The official ECMAScript decorators introduced in TypeScript 5.0, which are now part of the JavaScript standard. This warning specifically refers to legacy decorators, which are still widely used in frameworks like Angular, NestJS, TypeORM, and MobX. When TypeScript sees decorator syntax without the experimentalDecorators flag enabled, it issues this warning because decorators are not enabled by default.

Typical symptoms

• Warning message: 'Experimental support for decorators is a feature that is subject to change'
• Yellow/orange underlines in IDE on decorator syntax (@Component, @Injectable, etc.)
• Code with @decorator syntax triggers compiler warnings
• Build process completes but shows warnings in output
• Decorators appear to work at runtime but TypeScript complains during compilation
• IDE suggests enabling experimentalDecorators in settings

Common causes

1. Using decorator syntax (@decorator) without experimentalDecorators enabled in tsconfig.json
2. Missing or incomplete tsconfig.json configuration file
3. Using a framework that requires decorators (Angular, NestJS) without proper TypeScript setup
4. Compiling TypeScript files directly with tsc without loading tsconfig.json
5. IDE using different TypeScript configuration than build process
6. tsconfig.json exists but experimentalDecorators is set to false or omitted
7. Using multiple tsconfig files (like tsconfig.app.json) where experimentalDecorators isn't set in the active config

How to fix "Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option in your 'tsconfig' to remove this warning."

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

# Recompile your project
npx tsc

# Or restart your dev server
npm run dev

# WRONG - ignores tsconfig.json
npx tsc src/app.ts src/decorators.ts

# CORRECT - reads tsconfig.json
npx tsc

# Or specify the config file explicitly
npx tsc -p tsconfig.json

{
  "compilerOptions": {
    "experimentalDecorators": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

{
  "typescript.tsdk": "node_modules/typescript/lib",
  "typescript.preferences.experimentalDecorators": "enabled"
}

# List all tsconfig files
find . -name "tsconfig*.json" -not -path "*/node_modules/*"

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "target": "ES2021",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true,
    "skipLibCheck": true
  }
}

# Compile with experimentalDecorators flag
npx tsc --experimentalDecorators

# With emitDecoratorMetadata as well
npx tsc --experimentalDecorators --emitDecoratorMetadata

# Add to package.json scripts
{
  "scripts": {
    "build": "tsc --experimentalDecorators --emitDecoratorMetadata"
  }
}

Advanced notes

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

import "reflect-metadata";

class MyClass {
  @LogType
  myMethod(param: string): number {
    return 42;
  }
}

// At runtime, you can read the parameter types:
const paramTypes = Reflect.getMetadata("design:paramtypes", MyClass.prototype, "myMethod");
console.log(paramTypes); // [String]

const returnType = Reflect.getMetadata("design:returntype", MyClass.prototype, "myMethod");
console.log(returnType); // Number

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "module": "commonjs"
  }
}

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

{
  "compilerOptions": {
    "experimentalDecorators": true
  }
}

@Component({
  selector: 'app-root'
})
class AppComponent {}

class UserService {
  @Get('/users')
  findAll() {}
}

class User {
  @Column()
  name: string;
}

class UserController {
  create(@Body() userData: CreateUserDto) {}
}

npx tsc --version

ls -la node_modules/typescript

rm -rf dist/
rm -rf .tsbuildinfo

{
  "typescript.tsdk": "node_modules/typescript/lib"
}

Frequently asked questions

What does "Experimental support for decorators is a feature that is subject to ch" mean?

The "experimentalDecorators" warning appears when TypeScript encounters decorator syntax (@decorator) in your code but the compiler option to enable decorators hasn't been set. Decorators are a special TypeScript feature that allows you to add annotations and metadata to classes, methods, properties, and parameters. TypeScript supports two types of decorators: 1.

How do I fix "Experimental support for decorators is a feature that is subject to ch"?

This TypeScript warning appears when you use decorators without enabling the experimentalDecorators compiler option. The fix is to add 'experimentalDecorators: true' to your tsconfig.json compilerOptions.

What causes "Experimental support for decorators is a feature that is subject to ch"?

Using decorator syntax (@decorator) without experimentalDecorators enabled in tsconfig.json Missing or incomplete tsconfig.json configuration file Using a framework that requires decorators (Angular, NestJS) without proper TypeScript setup

Is the "Experimental support for decorators is a feature that is subject to ch" error serious?

It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

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Official resources & further reading

• 📚TypeScript Official Documentation
• 📖
  TypeScript TSConfig - experimentalDecorators(Official Docs)
• 📖
  TypeScript Handbook - Decorators(Official Docs)
• 📖
  TypeScript TSConfig - emitDecoratorMetadata(Official Docs)
• BobbyHadz - Experimental Support for Decorators Warning
• Medium - Solving Experimental Decorators Warning
• 🐙
  TypeScript GitHub - How to Set experimentalDecorators(GitHub)
• 🐙
  VS Code GitHub - Experimental Decorators Warning(GitHub)
• Refine - TypeScript Decorators in Brief