# Param

**Kind:** Function

**Source:** [`packages/common/decorators/http/route-params.decorator.ts`](https://github.com/nestjs/nest/blob/master/packages/common/decorators/http/route-params.decorator.ts#L689)

**Part of:** [Common](subsystem-packages-common)

Route handler parameter decorator. Extracts the `params`
property from the `req` object and populates the decorated
parameter with the value of `params`. May also apply pipes to the bound
parameter.

For example, extracting all params:
```typescript
findOne(@Param() params: string[])
```

For example, extracting a single param:
```typescript
findOne(@Param('id') id: string)
```

`Param()` binds route parameters from `req.params` to a controller handler argument. Pass a parameter name to extract one value, or omit it to receive the full params object; pipes can transform or validate the bound value.

## Signature

```ts
function Param(property: string | (Type<PipeTransform> | PipeTransform), pipes: (Type<PipeTransform> | PipeTransform)[]): ParameterDecorator
```

## Parameters

| Name | Type |
|---|---|
| `property` | `string | (Type<PipeTransform> | PipeTransform)` |
| `pipes` | `(Type<PipeTransform> | PipeTransform)[]` |

**Returns:** `ParameterDecorator`

## Diagram

```mermaid
graph LR
  Request[HTTP request] --> ReqParams[req.params]
  ReqParams --> ParamDecorator["@Param()"]
  ParamDecorator --> HandlerParameter[Route handler parameter]
  Pipes[Pipes, if provided] --> HandlerParameter
```

## Usage

```typescript
import { Controller, Get, Param } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get(':id')
  findOne(@Param('id') id: string) {
    return { id };
  }

  @Get(':userId/posts/:postId')
  findPost(@Param() params: Record<string, string>) {
    return params;
  }
}
```

## AI Coding Instructions

- Use `@Param('name')` when a handler needs one named route parameter.
- Use `@Param()` without a name when the handler needs the complete `req.params` object.
- Keep the decorator parameter name aligned with the route token, such as `@Get(':id')` and `@Param('id')`.
- Attach pipes to `@Param()` when route parameter values require validation or transformation before reaching the handler.